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THE famous American engineer, Mr. E. F. W. Alexanderson, has set up an apparatus for television, about which he is extremely optimistic.
His
theory, it is interesting to note, is based on the same principle as that of M. Edouard Belin, and seems somewhat different from that of the English inventor Baird, whose experiments have aroused so much attention.
Dr. Alexanderson's apparatus consists of the usual light beam thrown on to a rotating series of mirrors, which reflect this beam on to a screen in a little moving spot of light. But, where Belin used only one light source, and had only one light beam, Alexanderson has used seven. In this manner he develops a. useful illumination of 49 times that of Belin.
This was the great difficulty with Belin's work - he had to cover a screen with this one light spot about (according to Dr; Alexanderson's figures) 500,000 times in one second- a thing which is physically impossible with any clarity of detail. With the seven light sources this can be reduced to only 45,000 strokes per light beam- a modulation not beyond the bounds of reason, as it is only ten times as fast as that of radiotelephone broadcasting.
For distance transmission of pictures, telegraphic signals can be used, as they come in independent of signal strength, and thus are not affected by fading, according to Dr. Alexanderson. He adds that the short wave would, of course, be used in this work.
Alexanderson considers that actual television for the ordinary broadcast listener is quite a logical possibility; despite the difiiculties to be overcome.
N. C. MCL.
Image description:
AN AMERICAN TELEVISION DEVICE. Dr. E. F. W. Alexanderson, the well-known engineer, is seen pointing to the cluster of seven lights which make up an important feature of his television system. The drum in the foreground, which is made to revolve at very high speed, is fitted with 24 mirrors at slightly differing angles, with the result that the entire screen is covered with reflecte light in a fraction of a second.
IN contemplating the fascinating subject of television one is very soon brought to the point of wondering just how far we have actually succeeded along the path of solution of this problem.
If one goes solely by the popular reports which are published at frequent intervals, one is led to suppose that television is already accomplished, and that there only remain matters of minor detail to be attended to before a living cinematograph becomes a reality.
We cannot help feeling regret that in a matter of this kind, which is of such scientific interest, those who are working on the problem do not seem to realise the extent to which confidence in their inventive efforts, however humbly they may regard them themselves, is shaken when the inventor gives us a gilded story through the medium of an over-imaginative and perhaps wholly unscientific journalist who is far more concerned in being able to justify startling headlines than in giving the bare, and perhaps somewhat dry, facts with which he is supplied.
We believe that, although a good deal of interesting work is being done in the direction of solving the problem of television, yet up to the present little of real practical value has been achieved.
It is true that crude representations of objects have been reproduced over a distance by one or two different systems, but we have no proof as yet that any one of these systems is likely to produce results much beyond their present stage of development.
From the point of view of the scientiifc tackling of the problem, the most interesting of the methods recently discussed is no doubt that of Dr, Alexianderson, of America. Dr. Alexanderson appears to have a very thorough grasp of the problems involved and he has undertaken a series of experiments to ascertain what are the limitations of the apparatus at our disposal where-with the problem must be tackled.
We fully expect that if Dr. Alexanderson continues his researches with the unrivalled resources which are at his disposal, developments of first-rate importance are likely to result.
Phototelegraphy and Television
An Account of Dr. E. F. W. Alexanderson's Experiments
By A. DINSDALE.
CONTEMPLATION of the works of great imaginative authors inevitably leads one to the conclusion that the really great discoveries and inventions of our modern civilisation are first visualised by them long before they' become accomplished facts.
Jules Verne's descriptions of submarines and aircraft are cases in point. Under the stimulus of such imaginative writings it would appear that scientists then set about the business of making the author's dreams come true.
In the realm of television many fiction stories have been written in which television, in some form or another, has been brought in as an accomplished fact. An out-standing example of this is to be found in George Bernard Shaw's well-known play, "Back to Methuselah," in which is described a scene taking place in the year 2170, where the head of the British Government holds conferences with his Cabinet ministers several hundred miles away. At his desk is a switchboard, and in the back-ground is a screen upon which, when he selects the right key at the switchboard, a life-size picture appears of the man to whom he is talking, a picture which portrays faithfully all the movements of the distant minister.
Work Based upon Phototelegraphy
Taking this incident in Shaw's play as his text, Dr. E. F. W. Alexanderson, of the General Electric Company, Schenectady, N.Y., has embarked upon a line of experimental research to see if he cannot make Shaw's vision an actual demonstrable fact.
There is no reason why such an apparently impossible dream should not come true, and come true within a relatively short space of time.
It is not so many years ago since Owen D. Young, of the Radio Corporation of America, expressed, at a banquet, the hope that radio would soon give us visual means of communication. This idea seemed rather far-fetched to several technical men who were present, but work upon these lines was immediately started, and to-day there is a commercial wireless picture service in regular operation between London and New York.
It takes about twenty minutes to transmit one of these pictures across the Atlantic, whereas Bernard Shaw's imaginative scene foretells the direct vision of distant moving objects.
Our experience of the cinematograph indicates that in order to portray a scene in such a manner that all movement is faithfully reproduced, sixteen complete pictures per second must be flashed upon the screen.
Retentivity of Vision
Each succeeding picture is slightly different from its predecessor, and, due to the phenomenon known as retentivity of vision, the observer sees, not sixteen separate pictures, but one single picture full of smoothly flowing movement.
Thus, in order to achieve television, we must speed up our phototelegraphy system so that a single picture can he transmitted in one-sixteenth of a second instead of twenty minutes. From twenty minutes to one-sixteenth of a second is a tremendous stride, but one which Dr. Alexanderson has set about trying to make, starting with phototelegraphy as the art is already known to-day.
There is nothing particularly novel in Dr. Alexanderson's phototelegraphy apparatus, which is of the well-known revolving cylinder type. His researches in this direction have tended rather to investigate and solve the problems involved in the transmission of the picture impulses over great distances by wireless.
The Radio Link
Up to the present radio communication has been carried out by means of two distinct methods of signalling: by modulation and by interruption. The older of these two methods, and by far the more sensitive and economical, is that of interruption, and it has been developed to a high degree of efficiency.
The modulation method, on the other hand, is comparatively new, and not nearly so sensitive and economical. It is the method employed by our broadcasting stations, and for a given power the effective range of the modulated signal is only about one-third or one-quarter that of the interrupted signal.
Picture transmission by wireless has been tried by both these methods. The transatlantic picture service is operated by the interrupted method of signalling.
Dr. Alexanderson has experimented with both methods. Although better results appear to have been obtained by the modulation method Dr. Alexanderson states that his researches have tended to make him consider the adaptation of the telegraphic method of communication to picture transmission as one of the essential problems.
Only in this way, he thinks can the deleterious effects of fading and static be eliminated, and he has devised a method of sending half-tones which takes advantage of the more efficient methods used in radiotelegraphy. It is obvious that fading and static would seriously distort or mutilate a picture being sent by wireless over a great distance.
Dr. Alexanderson's method makes use of the latest devices of long-distance, high-speed radiotelegraphic practice, wherein it is equally important to prevent mutilation of signals in order that the automatic signal recording apparatus shall he able to produce unblemished records of the transmitted telegraphic signals.
Briefly put, radiotelegraph engineers overcome fading by using at all times sufficient amplification to produce a readable signal during the worst intervals of fading.
The output signal is prevented from rising above a predetermined value, sufficient for recording, during periods of strong incoming signals, by throttling it down by means of a circuit arrangement employing a limiting valve.
The output signal of the receiver thus remains constant at all times. Static is taken care of by introducing a threshold value of signal into the receiver, so that nothing is received unless the signal exceeds this value. In this way, so long as the signal strength exceeds that of the prevailing static, the effects of static are eliminated from the signal record.
Thus far it has not been possible to adapt these devices to modulation methods of communication, so that for picture transmission by wireless over long distances the interruption, or telegraphic, method is obviously better fitted to give unblemished results.
Producing Half-tone Effects
Dr. Alexanderson obtains half-tone effects by causing his transmitting mechanism to analyse the picture into five or more separate shades, such as white, light grey, medium grey, dark grey, and black. This is done automatically, and the receiving mechanism also reassembles the shades automatically.
Various methods can be designed for translating these different light values into radio signals. One method is to use a separate wavelength for each shade, requiring, in this case, five wavelengths.
A process which employs only one wavelength is accomplished by causing the transmitting mechanism, at every moment, to select automatically the shade that comes nearest to one of the five shades. A telegraphic signal is then sent out which selects the corresponding shade in the receiving machine. This process is not so complicated as it sounds, for the telegraphic code by which the various shades are selected depends upon the synchronism of the two machines, which synchronism is necessary under all circumstances.
Thus black areas in the picture at the transmitting end are reproduced at the receiver by exposure of the sensitive paper to the recording light spot during four successive revolutions of the paper-carrying cylinder. Light grey is produced by a single exposure during one revolution only, and no exposure during the three succeeding revolutions. It will be seen, therefore, that the receiving cylinder must be run at four times the speed of the transmitting cylinder, but with the same speed of axial movement.
The overlapping exposure is progressive and the whole thing is a continuous process, tending to graduate evenly the various degrees of light and shade in the picture.
Speed Limitations in Television
Turning now to the question of' television, Dr. Alexanderson queries whether the medium with which we are dealing is capable of functioning at the enormous speeds of signalling required in television work. Necessary units in the system are the photoelectric cell, the amplifier, the aerial and the wireless wave. Of these, the first two employ the medium of the electron, which is extremely fast ; but the use of wireless waves imposes certain speed limitations on account of the limited number of wave-lengths available.
The lines upon which Dr. Alexanderson is working appear to indicate that, in order to obtain high quality reproduction of a television image, it will be necessary to make use of several wavelengths, each carrying an imperfect image. At the receiving end all these imperfect or crude images will be combined to produce a single image of high quality definition.
This conclusion has been reached as a result of some experiments made in the transmission of single pictures at different speeds on a single wavelength of 12,000 metres, or 25 kilocycles. Pictures sent in two minutes were reproduced somewhat crudely; those sent in four minutes very much better, and when the time of transmission was extended to eight minutes for the same picture the reproduction was well-nigh perfect.
[ The modern words are not available at this time, but there is mention above of definition. The text also refers to what we would consider "sample rate" and "bit rate", which is affected by all stages of the processes used].
The relative difference in definition between these pictures is due, according to Dr. Alexanderson, to the effect of the sluggishness of the tuned transmitting aerial. The two-minute picture was not nearly so sharp as the eight- minute picture, but was, nevertheless, sufficiently so to be acceptable for ordinary television purposes, supposing such a degree of definition could be obtained at television speeds of transmission.
Since there is so much sluggishness on a wavelength of 12,000 metres, let us examine the effect of reducing the wavelength to 12 metres, equivalent to a frequency of 25,000 k.c. If the photoelectric cell, amplifier and the light control can keep up with this enormous frequency, the wireless wave will perform its task and transmit a single picture, the definition of which will be equal_to the two-minute picture as transmitted on the longer wave, in one-thousandth part of two minutes, i.e. in approximately one-eighth of a second. This is not equivalent to cine matograph speed, but it is sufficiently close to give us a fairly good picture.
Another difficulty, where a life-size television image is required, as suggested by Bernard Shaw, is in sufficiently illuminating the screen at the receiving end in the extremely limited amount of time available.
In any television receiver so far developed or suggested, the incoming picture impulses control the degree of brilliancy of a source of light which is focussed upon the screen and caused, by optical means, to sweep rapidly up and down and across the screen, gradually covering it all with varying intensities.of light. In order to give the observer the impression of a complete picture this traversal of the screen must be arranged to take place practically instantaneously otherwise the observer would see what actually occurs- a spot of light gradually crossing the screen as it swings rapidly up and down.
In order to get an image of fair quality the least we can be satisfied with is ten thousand different values of light intensity. This may mean that the spot of light will pass across the screen in 100 parallel paths, each being sub-divided into 100 different light values.
If this process is repeated over and over again at the moving picture speed of sixteen separate pictures per second it means that 160,000 changes of light value, or pictufr impulses, are required per second.
Such a speed seems, on the face of it, inconceivable. Moreover, a good picture really requires an elemental basis of more than 100 lines, so that a more suitable speed for the light impulses would be somewhere about 300,000 per second !
Not only must we employ wireless waves capable of such an enormous speed of signalling, but we must also employ a source of light of such brilliancy that it will illuminate the screen effectively, even though it has only one 300,000th of a second in which to illuminate any one given spot.
Dr. Alexanderson admits that, given the most brilliant arc lamp we know of, no matter how we design the optical system for sweeping this light across the screen, we cannot obtain sufficient brilliancy to illuminate a large screen with a single spot of light.
Dr. Alexanderson's Experimental Television Projector
For the purpose of examining this particular problem and attempting to solve it, Dr. Alexanderson has built an experimental television projector consisting of a source of light, a lens and a revolving drum carrying a number of mirrors.
The drum is built after the style of a flywheel, about 30 inches in diameter, with a flange about ten inches wide, around which are mounted twenty-four mirrors each measuring about eight inches by four. This drum is direct-coupled to a high-speed electric motor.
When the drum is stationary a spot of light is reflected on to the screen, which is about four feet square, and this spot of light is the brush that paints the picture. As the drum revolves the light spot passes vertically across the screen, and then, as a new mirror, set at a slightly different angle, comes into line, the light spot passes across the screen again, but on a track closely adjacent to that of its first traversal.
This action goes on until the entire screen has been covered. Such mirror mechanisms have been used by several television workers, and there is nothing about this one which is of particularly novel in terest.
The novelty of Dr. Alexanderson's experiments lies in the method being tried by him to overcome the difficulty of sufliciently illuminating a large screen in the extremely short period of time available.
As explained above, it is impossible to do this by means of a single spot of light, using any known methods of illumination and optical distribution of the light beam, so Dr. Alexanderson has been experimenting with seven light spots instead of one, for by so doing 49 times as much useful illumination can be obtained.
At first glance it is not easy to see why the gain in light should be as the square of the number of light. spots used, but on consideration it will be seen that, with one light spot in use, and a drum carrying 24 mirrors, the spot of light will pass over the screen 24 times. If seven light sources and seven spots of light are used, however, there will he a total of 168 light-spot passages over the screen for every revolution of the drum.
Multiple Light spots
The advantage of using seven beams of light in this fashion is two fold. First of all there is a direct gain of illumination of 7 to 1. Secondly, there is the further advantage that the speed at which the light beam must travel over the screen can be reduced approximately one- seventh, for each individual light spot now has only 24 tracks to cover instead of 168.
Although the light itself may travel at any conceivable speed, there are limitations to the speed at which the mirror drum can be driven. This also holds good for any other mechanical method of causing a light beam to traverse a screen. The mirror drum used by Dr. Alexanderson has already been designed to run at the highest possible speed.
The only way to speed up the movement of the light beam, therefore, would be to reduce the diameter of the drum and also the size of the mirrors, but mirrors one- seventh as large as those at present in use would only reflect one-seventh as much light and thus neutralise the advantage gained by using seven light spots instead of one.
There is another advantage arising out of the use of the multiple light beam. Since each individual light-spot need only move at one-seventh of the speed necessary when a single spot only has to cover the entire screen, the total number of light impressions to be made on the screen can also be divided up amongst the seven beams.
As described above, it is necessary, for a well-defined picture, to make at least 300,000 light impressions on the screen per second. If only one light-spot is employed it must be capable of handling this enormous number of light changes. By using seven light-spots, however, each individual beam need handle only 43,000 impressions per second.
A modulation speed of 43,000 per second is high, according to our present radio practice, but it is more within reason than 300,000, being only about ten times as high as the speed we use in broadcasting.
There is yet another point in favour of the multiple beam system. It is easy to design a television system that will give something like 40,000 picture units per second, but the results would be so crude as to have no practical value, for work already done on phototelegraphy has shown that at least 300,000 units per second will be necessary to give satisfactory results for television purposes.
This speeding-up process, unfortunately, is one of those cases where the difficulties increase as the square of the speed, and the main cause of the trouble is the fact that we have to depend upon moving mechanical apparatus. If some means were available for sweeping a beam of light across a screen at ultra-high speed without the use of mechanical apparatus, the problem would be easier of solution.
But such means are not available at present, so the ideal picture on a large screen, containing at least 300,000 picture units, cannot be obtained by means of mechanical apparatus and a single light-beam.
Dr. Alexanderson's way out of the difficulty, then, consists of reproducing on the screen seven crude pictures, containing only 40,000 picture units each, and so inter-lacing them optically that the combination effect is that of a single good picture containing 300,000 units.
In his experimental projector Dr. Alexanderson has arranged his seven light sources close together in star formation, so that the multiple beam, when seen stationary upon the screen, shows seven points of light arranged like the end section of a piece of seven-stranded wire.
Tests have been made with this model television projector to demonstrate the method of covering the screen with seven beams working simultaneously in parallel.
As the mirror drum revolves, these seven beams trace seven lines at once on the screen, and then pass over another adjacent track of seven lines until the entire screen has been covered.
In a complete television apparatus, of course, each of the seven light-spots would have to be independently controlled by the distant transmitter, so that each traced its own individual crude picture. For this purpose seven photoelectric cells would have to be arranged in a cluster at the transmitter, each cell controlling one channel of a multiplex radio system.
Seven Channels Required
For this purpose Dr. Alexanderson suggests that a Hammond multiplex system could be used with seven intermediate carrier waves, which, as he puts it, are "scrambled" and sent out by a single transmitter, and unscrambled at the receiving station so that each controls one of the seven light beams.
He further suggests that seven television carrier waves may be spaced 100 kilocycles apart, so that a complete television wave-band should be 700 k.c. wide. Such a radio channel might be placed between 20 and 21 metres. and he is of the opinion that if the use of such a wave-band will enable us to see across the ocean it will be assigned to a worthy purpose.
No details of Dr. Alexanderson's transmitting mechanism are available, and he lays no claim to having completely solved the problem of television. He merely states that "Our work has, however, already proved that the expec tation of television is not unreasonable, and that it may be accomplished with means that are in our possession at the present day."
THERE is a good deal of misunderstanding in the public mind as to the actual progress made in television, said Mr. A. L. Rawlings, of the Admiralty Research Department, in an address before the members of the Windsor and Eton Scientific and Archaeological Society.
The sounds of a whole orchestra can be reproduced by the vibration of a single telephone diaphragm, but there is very much more involved in television.
To transmit an object; a person, or a scene, every separate bit must be faithfully reproduced by a single transmission.
An experiment was shown in which, by means of two valves and two mechanical relays, the current through selenium could be amplified about a million times, to light an lamp, when the selenium was illuminated.
When pictures were transmitted by telegraph or wireless a scanning cell and lamp passed over photo paper moving in synchronism with another recording instrument which reproduced a picture.
In ten or fifteen minutes a very good reproduction could be made. There were about 10,000 small dots in an ordinary Press portrait. The scanning cell had to travel all over the picture to take up these elements. It was considered that a face could be transmitted by 5,000 elements as it minimum.
If they could transmit in this way a succession of instantaneous photographs much more quickly, we should be getting on to television.
It was this rapidity of transmission that constituted the chief difficulty.
After demonstrating the transmission of one small detail, he said that, so far as he knew, they had seen in this experiment the most complete demonstration of television that had ever been made in public.
As a serious solution to television nothing we had as yet seemed of great promise. It could not be said to have reached success even in the hands of experts, and would require enormous development before it could come into practical operation.
Television must be classed as one of the problems, like the nature, and cure of cancer, which, after baffling mankind for a generation, still eluded us. At the same time scientific experts were accumulating useful facts, and television might yet be realised.
TELEVISION DEMONSTRATION IN NEW YORK
In a square of glass 2 by 2 inches across, a group of Press representatives at the Bell laboratories in New York saw the figure of Mr.Hoover, the U.S Secretary of Commerce in Washington, speaking on the telephone 200 miles away.
This successful demonstration of television was carried out on April 7th 1927 and was organised by the American Telephone and Telegraph Company. The experiment was first performed on the telephone line, but subsequently the party witnessed a number of vaudeville turns transmitted by wireless from the Whippany broadcasting station, New Jersey.
For the benefit of a large audience, the pictures on the small glass square were projected on to a screen, and although the definition on the screen was not so clear it was generally agreed that the demonstration was a remarkable success.
The person whose picture was transmitted (says the Times New York correspondent) sat in front of a cabinet containing three large photo-electric cells, each 15in. long. Across the subject's features ran a beam of light directed to successive points by a rotating reel, with 2,500 points pierced in the edge, in such a manner as to direct the beam to every part of the feature.
The changing currents set up in the photo-electric cell were amplified 5,000,000,000 times before transmission. So clear was the picture on the receiving`screen that it was possible to distinguish the person's teeth and the ash on the end of a cigarette.
[Technical description from above AT&T website: "Television in those days was mechanical. Hoover was scanned by a narrow beam of light passing through tiny holes in a large, spinning disk that was set in front of his face. The image appeared in New York as tiny dots of light on the 2x2.5 inch face of a neon glow lamp. The cathode ray tube hadn't been invented yet." The picture was at 16 frames per second with a resolution of 50 lines- compare to the Baird 30 line mechanical system first introduced in England]
TELEVISION.
IN this issue we publish the first detailed account of what is, without question, the first successful public demonstration of television.
The article provides a fascinating story, indicating the extent to which science has brought us in the direction of achieving what, a year or two ago, would have been regarded as an impossibility.
It is clearly pointed out by those responsible in America that this demonstration must not be regarded as a service which promises early commercial practicability.
The demonstration was carried out irrespective of cost and complexity of the apparatus; for the purpose of carrying out the experiments nearly one thousand men were employed, and when the transmission was conducted by wireless three wavelengths had to be utilised ; but television has been successfully demonstrated, and the task of the future is to simplify the methods by which it is achieved.
A Successful Public Demonstration of Television between Washington and New York.
Article By A. DINSDALE.
FOR some time past great interest has centred round the problem of television-- seeing at a distance by telegraphy, either wire or wireless.
Ever since the discovery of selenium by May in 1873 television has been the dream of scientists all the world over, and of recent years more and more research workers have entered this fascinating field, until there is now an international race for final success along practical lines.
The latest experirnenters to enter the field are a group of engineers associated with the great American Telephone and Telegraph Co., one of America's largest industrial companies, which depends for its scientific progress upon vast organised laboratories staffed by some of the cleverest telephone and radio engineers in the world.
A group of engineers attached to these laboratories (The Bell Telephone Laboratories, Inc.) have been working away quietly on the problem for some years, until, on April 7th last, they were able to give a public demonstration of television over both wire and wireless circuits.
This demonstration was given before a party of guests which included business executives, newspaper editors, engineers, and scientists. The party assembled at the Bell Telephone Laboratories in New York, and were enabled to speak to, and simultaneously see, friends over the ordinary long-distance telephone line to Washington, 200 miles away.
In his introductory remarks Walter S. Gifford, President of the American Telephone and Telegraph Co., stated that "the elaborateness of the equipment required by the very nature of the undertaking precludes any present possibility of television being available in homes and offices generally. What its practical use may be I shall leave to your imagination."
Mr. Gifford then introduced Dr. Herbert E. Ives, under whose direction the research work on television has been carried out. Dr. Ives then gave the party a brief lecture, in the course of which he outlined the details of the invention, and gave a demonstration of its operation between one end of the laboratory and the other. In this demonstration he was assisted by Dr. Frank Gray, who is responsible for several of the developments which made possible the complete system.
Following this demonstration Mr. Gifford then talked over the telephone with General John J. Carty, vice- president of the company, who was in Washington, and afterwards with Secretary Hoover, of the Department of Commerce.
As Mr. Gifford talked to the General the latter's face became visible on a small screen, measuring about two inches by three inches, which was mounted in front of Mr. Gifford's telephone.
"How do you do, General? You are looking well" said Mr. Gifford.
The face of General Carty smiled and his voice enquired after the health of the speaker on the New York end.
"You screen well, General," said Mr. Gifford. "You look more handsome over the wire."
"Does it flatter me much? " General Carty asked
"I think it is an improvement;" was the reply
Loud-speaker and Large Screen
Mr. Hoover was then called to the telephone, and his speech was made audible to the assembled guests by means of a loud-speaker, whilst the distant speaker was rendered visible on a large screen for auditorium use, measuring about two feet by three feet.
This large illuminated transparent screen seemed some- what corrugated. This was due to the fact that the squares which make up the picture are arranged in 50 rows; one on top of the other.
As the eye became accustomed to looking at the screen in the darkened room the face was easily recognisable, although the features, which had been sharp and distinct on the miniature screen for individual use, had become considerably blurred by the enlargement.
It was plain that, enlarged to the size of an ordinary motion picture film, the detail would have been completely lost. The invention is admitted to be far from the motion picture-house stage.
The images reproduced upon the small screen have been described as being comparable to excellent daguerreotypes which have come to life and started to talk. In these small pictures the detail of the face appears in clear-cut black lines against a shining gold background, which is due to the orange light from the neon tube which is used in reproducing the small images.
During this demonstration the pictures were projected only one way-from Washington to New York- it having been considered unnecessary for the purpose to establish two-way television-telephone communication, but there is no technical reason why this could not have been done had it been so desired.
Television by Wireless
Following the wire demonstration between New York and Washington the visitors were entertained to a repetition of the experiments, the transmission on this occasion being by wireless from the company's experimental station, 3XN, at Whippany, N.J., about 30 miles from New York.
The first face to appear upon the screen was that of an engineer, who gave a technical description of what was taking place. Next came a vaudeville act by a comedian, followed by a regular radio programme item- a short humorous dialect talk by a lady. Before and between the acts the announcer of the Whippany studio made a television appearance during announcements.
An important feature of these demonstrations was that there was no difference in the quality of the reproduced image, whether it was transmitted from one end of the laboratory to the other, by wire from Washington, or by wireless from Whippany.
The engineers responsible for this latest scientific development are well aware, and have made no secret of the fact, that one of the serious problems in perfecting the invention for general commercial use is that of cost.
For the purpose of the demonstration on April 7th when Secretary Hoover in Washington was seen and heard in New York, nearly 1,000 men were required.
Furthermore, the transmission of television requires the use of a large group of frequencies, and the transmission of these frequencies requires a considerable number of ordinary telephone circuits.
In the case of the transmission of television by wireless, utilising the system under review, one wavelength is used for sending the picture and two for the synchronisation process. Dr. Ives himself emphasised the difficulty here, in view of the congested condition of the ether.
No new principles are involved in this latest television development; many old principles have simply been applied under the guidance of recently acquired scientific knowledge. Principal in all this has been the knowledge obtained during the past few years in the research and development which has made it possible for the American Telephone and Telegraph Co. to augment its national telephone service by a transcontinental phototelegraphy service.
Television and the transmission of pictures by wire or wireless have many points in common. In an electromechanical system of picture transmission it is not possible to send the entire picture at once; it has to be sent over the circuit, or through the ether, piece by piece.
Similarly, in television, the scene to be transmitted must be carried over the transmission circuit bit by bit, and the received picture recreated bit by bit.
In the case of television, however, and in contrast to phototelegraphy, the details transmitted must follow each other so rapidly that to the eye and brain of the observer at the receiving end the effect will be that of seeing the scene reproduced as a whole, complete with natural movement.
This effect is rendered possible of achievement by what is called retentivity of vision, which means that the eye retains for an instant the impression of an object which it has seen after the object itself has been withdrawn from the actual field of vision.
Broadly speaking, the apparatus for television consists first, of an electro-optical device substituting for the eye, which "looks at"” the scene to be transmitted.
Viewing a small portion of this scene at a time, it transforms the variations of light and shade which it sees into variations in the strength of an electrical current.
The next factor is the transmitting medium, which may be either a wire or a wireless circuit.
The third factor is the receiving apparatus by means of which the variations of current may be transformed back into terms of light and shadow, and the picture thus reconstructed piece by piece.
The fourth and final factor is the apparatus used to keep the sending and receiving mechanism in step.
The Transmitting Mechanism
An essential feature of all television transmitters is that the scene to be transmitted must be illuminated. The intensity of the illumination depends largely upon the sensitivity of the light-sensitive device used to transform the light impulses into electrical impulses.
With all systems so far developed it has been customary to flood the entire scene with light, and this light, in most cases, has had to be so intense as to cause considerable discomfort to any person facing it. The intensify. of the light has had to be made so great because, when an alkali photoelectric cell is used as the light sensitive device, its response to light impulses is extremely feeble, the output requiring enormous amplification before it will perform the work required of it.
It must be borne inf mind that the light which reaches the cell is reflected light, and some idea of the feebleness of reflected light may be obtained from the calculation of one scientist who estimates that, if the human face is illuminated with a 1,000 candle power lamp, the total amount of light reflected from it will scarcely amount to ONE candle power.
In the matter of intense illumination the television system under review is no exception. Photoelectric cells are dsused to transform the light impulses into electrical currents, and a very intense illumination is employed, which is provided by means of arc lamps.
Unlike other systems, however, the scene to be transmitted is not constantly flooded with this great light. Between the arcs and the scene there is interposed a revolving disc which has drilled in it, near the circumference, a series of small holes which form a single spiral. Through these holes there shines, at any given moment, only one single spot of light.
The rotary action of the disc causes this spot to travel from left to right across the scene or individual to be transmitted, then the next hole, set a trifle nearer the centre of the disc, allows another spot of light to pass through, which travels across the scene on a parallel track, but a trifle lower down than did the last one. As the disc continues to. rotate, this action continues till the entire scene has been covered, or explored.
The Photoelectric Cells
The disc rotates so rapidly that the whole scene or object is lighted up, a little spot at a time, in less than a fifteenth of a second. There are fifty holes in the disc, so that the scene has fifty illuminated lines traced across it.
By this method an intense illumination of the sitter can be obtained without undue discomfort. All that can be seen is a flickering spot of light which crosses and re-crosses the sitter's face at an incredible speed. Even when using this method of illumination, however, it is said that the sitter begins to feel discomfort after a few minutes' exposure to the intense light spot.
The lines, contours, and colours of the face of the sitter cause variations in the degree of brilliancy of the spots of light they reflect, and these, in turn, cause, a similarly varying effect where they strike the photo-electric cells.
The light spot which covers the scene to be transmitted shines out from the cavity in the middle of the box-like arrangement before which the figure is sitting. Around this cavity, behind the metal screens, are placed three huge photoelectric cells. In the photograph in the title of this article Dr. Ives can be seen holding one of these. They are probably the largest photoelectric cells ever made.
The ability of these cells to conduct electricity varies in direct proportion to the light falling upon them. As any particular part of the object is illuminated by the travelling spot of light, the flucuations of current thus produced are transmitted, after amplification, to the receiving apparatus
As has already been explained, the total amount of light reflected from a human face is very small indeed. Coupled with this there is the well-known fact that the electrical output of a photoelectric cell is extremely minute, and requires considerable amplification before it can be utilised to operate a circuit. The current which was sent out by radio at Whippany, for example, had to be amplified 5,000 million million times before it was broadcast from the antenna!
Increasing Sensitivity to Light
Hence the reason for such large cells. Three are used in parallel, partly to augment the total response and partly to secure the effect, by virtue of their arrangement, which would be obtained if the sitter were flooded with light from three directions- from above, from the right, and from the left.
As each detail of the sitter is illuminated, the photo electric cells instantly respond, initiating a current proportional to the light reflected to them, and hence proportional, to the light and shade of the particular detail. As the beam of light swings across the scene, working its way from top to bottom, the current from the cells varies correspondingly.
So swiftly does the beam sweep the scene that the current variations are wide and rapid- sometimes corresponding to a change from a maximum current to a minimum and back to a maximum in a twenty-thousandth of a second. These variations, the so-called alternating current components, comprise the electrical impulses which are transmitted to the distant receiver. The speed of signalling is therefore about 20,000 per second.
At the Receiving End
Two forms of receiving apparatus have been developed. In both forms of receiver a neon gas tube is an im portant element. Such tubes, which the reader has no doubt seen used in advertising display devices, are hollow glass vessels in which the air has been replaced by neon gas at a very low pressure. Electrical discharges passing through such a tube cause it to glow, the brilliance of the light being directly proportional to the strength of the current.
It will at once be appreciated that, in regard to the relation between light and electricity, the properties of a neon tube are exactly opposite to those of a photo-electric cell.
In the apparatus for use by a single individual a small neon tube is used, and the entire tube glows in accordance with the strength of the current being received from the transmitting station at any particular instant. Between the tube and the observer, who looks through a small aperture about two and a half inches square, there is interposed a disc exactly similar to the one at the transmitting station, rotating in step with it.
The result is that the observer sees at successive instants successive portions of the field of view, each of which is illuminated by the glowing neon tube, the brilliance of which is constantlv fluctuating.
So rapidly is the scanning of the field of vision carried out that the observer's sensation is that of seeing the scene as a whole recreated just as it .appears at the transmitting apparatus. What the observer would actually see if the mechanism were suddenly stopped dead would be a tiny spot of light, admitted to his line of vision through one of the holes in the disc. At each instant the position of this spot of light is caused to correspond to that of the detail of the scene at the sending end.
The entire scene, in successive details, is thus reproduced for the observer, and the complete process of reproducing in proper order the light details of the scene occupies less than a fifteenth of a second. It is then automatically repeated, so that the observer views the complete scene fifteen times per second, which, due to retentivity of vision, gives. a motion picture effect.
The Large Screen
For the presentation of the image to a large audience a different method must be employed. Instead of using a relatively small neon tube, successive portions of which are viewed at successive intervals, a very long tube is employed which is folded back and forth upon itself to form a grid. A near view of one of these grids, taken during the pumping process, is shown below.
The tube is bent into fifty loops, corresponding with the number of holes in the scanning disc at the transmitting end. Instead of being fitted with a single pair of electrodes, like the smaller tube, this grid is equipped with 2,500 electrodes, fifty per loop.
Each electrode corresponds to a single elemental area of the picture plane which is scanned by the photoelectric cells at the sending station. These electrodes are connected by wires to a distributor which, in turn, is connected to the circuit coming from the transmitting station. The distributor revolves in exact synchronism with the rotating disc at the sending end.
When a particular spot on the object at the sending end is illuminated, its position and light intensity are transmitted, in the form of an electrical impulse, to the receiving station, as has already been described. . In this case, however, the distributor selects the proper connection witb the neon tube and lights a spot on the grid corresponding with the spot on the original scene, the illumination of which set up the impulse.
Only one spot on the grid is illuminated at a time, but these glowing spots follow each other with such rapidity that the audience sees the entire grid lighted up, its degrees of illumination corresponding with those of the original scene, thus producing a complete picture before the eyes of the spectators. The grid may be viewed directly or through a screen of ground glass or other translucent material.
The distributor consists of a brush contact which is revolved in synchronism with the scanning disc at the sending end. This brush, as it revolves, makes contact with a commutator arrangement, composed of 2,500 segments, to which the leads to the neon tube electrodes are connected.
Each segment picks up from the rotating brush the appropriate electrical impulse intended for it, and conducts it over the connecting wire to the appropriate electrode on the grid. To each one of the 2,500 wires 15 impulses per second must be delivered. The most minute error would scramble the portrait completely.
Synchronism
The question of synchronism is of vital importance in any television system. The mechanism at both the transmitting and receiving ends of the circuit must run exactly in step. . In this latest system dots of light are put together at the rate of about 45,000 a second to give the effect of a motion picture.. Each dot has to be in its exact place.
The mosaic of' dots, or picture elements, would be a jumble-- the picture would be completely pied -if there was an error of 1/90,000th part of a second in the synchronisation between the sending and receiving apparatus.
The moving parts at each end of the circuit are driven by exactly similar motors, and, to ensure steadiness, two motors are used at eachend. One of each pair of motors is a synchronous alternating current motor, the function of which is to control the speed of the main driving motor.
The main motor operates at a frequency with which complete images of the scene can be formed. To prevent this motor from hunting, that is, from varying slightly in speed alternately above and then below that corresponding to 18 cycles per second, the second and smaller motor assists the drive.
This synchronous motor, operated at 2,000 cycles, in the range of telephonic rather than power frequencies, ensures that the rotating mechanisms at the two ends of the system shall not be out of step with each other by more than the amount represented by half of one of the small holes in the disc. This corresponds to an interval of time of 1-90,000th of .a second.
Success the Result of Co-ordinated Research
The successful development of this system of television is not the isolated work of any one man; as already stated, many engineers took part in the necessary researches, and their method of attack and the record of progress forms an interesting story in itself.
Dr. Ives, who was put in charge of the work, has many outstanding achievements to his credit, amongst them being the first practical lamp for producing artificial day-light. Throughout his career his researches have many times touched upon photoelectric cells and their various uses, and to him is due the work upon photoelectric cells in connection with the development of television.
Prior to commencing work upon television, Dr. Ives was engaged upon phototelegraphy, and it was he who developed the system which is now in daily use by the American Telephone and Telegraph Co. for the transmission of commercial and Press pictures to all parts of the United States.
This method of directing the research attack to the elemental phases of the problem is illustrated by the investigation of methods for producing currents in response to light variations and lights in proportional response to currents.
This was separated from the other investigations (such as those of methods for synchronisation and of the characteristics of transmission channels) by driving on the same shaft the scanning disc and the similar disc for reproducing, and thus operating the transmitting and re- ceiving equipment in close proximity.
In a later form of experiment a stage of final accomplishment was reached which might seem to have justified publication, but was withheld therefrom as being only a step in the research programme.
Cinematograph Films Transmitted First.
In this experiment a strip of motion picture film was projected from a standard projector upon a photo- electric cell, and the moving picture of this filrn was then recreated for an observer by means of a receiving equipment involving the use of a suitable neon tube and a scanning disc as already described earlier in this article.
This apparatus eliminated the problem of the illumination of the scene, for the photoelectric cell was influenced by directly transmitted light, which could be made as powerful as desired. This line of experiment thus permitted concentration on the other phases of television. Its adoption facilitated very much the study of synchronous motors, which were then developed under the direction of Mr. H. M. Stoller, whose work has for many years been connected with the exact regulation of the speed of electric motors.
To the apparatus for talking motion pictures, known as the Vitaphone, Mr. Stoller contributed the speed- control and synchronising devices, embodying the first commercial application of the thermionic valve for speed regulation. This method has a much higher precision than any other.
The Development of Scanning Devices
One of the next developments was that by Dr. F. Gray, a member of the technical staff of the Laboratories, who had previously been responsible for certain early forms of the experimental apparatus. He devised the method of projecting a minute spot of very intense light upon the object to be transmitted, and of moving this spot back and forth to illuminate successively the details of the entire area.
Following the development of this method, Dr. Ives constructed and arranged the large photoelectric cells which have previously been described.
Other phases of the research problem were met in the development by Dr. Gray of the large neon tube for the production of an image large enough to be viewed by a considerable audience, and the development and use of such a tube, with its present total of 2,500 external electrodes,- required the development also of the current distributor from which 2,500 wires, like a gigantic optic nerve, extend to the tube.
Dr. Gray is responsible also for the application to television of the basic principles of amplifier design.
As the terminal apparatus approached its present form there were studied other problems which were to be encountered in the transmission of the light-generated and synchronising currents over great distances, both by wire and by wireless. To transmit an image formed by 2,500 elements requires a channel capable of carrying without distortion the entire range of frequencies from 18 cycles per second to about 20,000 cycles per second. In order to give a high-grade telephone line such an extended characteristic, special equipment for the equalisation of attenuation and of phase shift had to be devised.
Similar problems in radio equipment were also solved by new designs and adaptations arising from the underlying researches, and these developments of wireless equipment resulted in an operative radio-television system of equal reliability to the wire-connected system.
When, according to the most conservative judgment of the-scientists concerned, and of the Laboratories' executives, the experiments had progressed far enough to assure operation over long distances both by wire and by wireless, field experiments were undertaken, and these experiments finally led up to the successful public demonstration of long-distance television described at the beginning of this article.
A number of instrument-making firms showed resistance boxes, ammeters, voltmeters, etc., and the B.B.C., in a special room showed what could be done in the way of good quality reproduction from the local station.
The exhibit which attracted the most attention was that of the Baird Television Development Co., Ltd., to whom were allotted several rooms in a separate building. The programme announced that Television, Noctovision, and the Phonovisor would be demonstrated by Mr Baird, but this proved too ambitious an undertaking. A very successful demonstration of noctovision between two rooms separated by an intermediate room was given to large numbers of the members , who passed through in batches hour after hour, and left Mr Baird and his staff little time for anything else.
A special demonstration of television and noctovision between London and Leeds was to have been given before twenty selected members of the Association on the evening of Monday, September 5th, but although Mr Baird himself went to London to superintend the transmitting end, successful transmission was not obtained, and the waiting scientists were dismissed with regrets.
We understand that the Phonovisor was not shown in operation, but was explained in principle by Mr Baird at a conversazione held at the University.
At the receiving end the audience is in darkness whether for television or noctovision, and sees the subject on a screen across which a light sweeps in synchronism with the sweep of the lenses at the transmitter; this light being obtained from a neon lamp is red, and follows in intensity the fluctuation of intensity of brightness of the subject.
The impression is somewhat similar to that of a very slow moving cinema picture. At Leeds, owing to the temporary character of the installation and the absence of concrete foundations for the motors, the speed was exceptionally low, and the flicker effect consequently enhanced.
We noticed a peculiar effect which we at first put down to a fading of the picture, but which we found was an optical illusion; if one allowed ones eyes to focus on the red light sweeping across the screen, and followed it across the screen, the picture vanished; it seemed necessary to ignore the sweeping light and look, as it were, beyond it to infinity; the picture then showed clearly.
In this way one could clearly detect when the person whose face was being transmitted opened and closed his mouth, or lit a cigarette, the smoke being clearly visible, in spite of the fact that the infra-red rays are supposed to penetrate fog.
Apart from the inconvenience of dazzling the 'patient' we do not know what are the relative merits of television and noctovision, but the latter is certainly the greater scientific novelty, and was far and away the most striking application of science to be seen at the Leeds meeting. It reflected great credit on those who were responsible for it.
We do not know, however, whether it represented conditions exactly as they would be between two distant stations. At Leeds the sending and receiving rooms were apparently separated by a very short distance, which would greatly simplify the problem of synchronisation, or do away with it entirely if a single motor could be used to drive both transmitter and receiver.
The apparatus which has been called a phonovisor differs from that described above in that the currents from the light sensitive cell are made to actuate, after amplification, the cutter of a phonograph recorder. By playing this record a sound is obtained which has been called the sound of a persons face, assuming a face to be the subject transmitted. Even the most beautiful face treated in this way sounds somewhat commonplace, and as a method of storing a moving picture it appears to be very far behind the film.
Although, to quote Mr Baird, 'if this record is played into a televisor, the original moving scene which caused the sound is reproduced on the screen of the televisor'. We doubt whether such a cycle, even with the possibility of having the scene and the voices recorded on the same cylinder or disc, can be improved and simplified sufficiently to be more than a scientific novelty. However, scientific prophesy is a dangerous past-time, and we will close by congratulating Mr. Baird on providing what was undoubtedly the most popular of the scientific exhibits at the Leeds meeting.
[to see a Baird disc and view a Baird moving image, visit the Bradford Museum of Photography etc. Or try a web site which has the images-tvdawn- Baird TV from archive.org]
While I personally admire what Mr. Baird has done in forwarding the art of television, nevertheless I think, in fairness to the facts, that Mr. C. Francis Jenkins is entitled, probably more than any other man, to credit as the earliest successful worker in this important research.
I am forwarding some clippings from papers of several years ago which testify as to these facts, which I know will be of interest to your magazine.
John Hays Hammond, Jun.
Gloucester, Mass, USA. September 7th 1927.
clipping:
WASHINGTON Sunday June 14th 1925:
First motion pictures transmitted by radio are shown in Capital
Government officials and scientists, summoned quickly by telephone, view successful experiment in Laboratory of C. Francis Jenkins. Small apparatus functions perfectly.
A group of distinguished government officials and scientists, called unexpectedly from their offices and laboratories, sat yesterday morning in the laboratory of C. Francis Jenkins, at 1519 Connecticut Avenue Northwest, and saw for the first time in history moving pictures of a moving object miles away , received over the radio and thrown upon a miniature screen.
Among the visitors who had been called hurriedly on the telephone by Mr Jenkins when he found the machine functioning perfectly , and who visited the laboratory at various hours in the morning, were Secretary of the Navy Wilbur, Dr D K Burgess, director of the bureau of standards, Stephen P Davies, Acting Secretary of Commerce, W. D. Terrill, of the radio department of the Department of Commerce, and two San Fransisco scientists who heard of the experiments and accompanied the officials to the laboratory.
Although the image broadcast was devoid of dramatic interest of itself, being a small model windmill with the blades in motion... [clipping has been cut here on republication, and continues... ]
...NOF, the old naval radio station which was turned over to Mr Jenkins for experimental purposes when the department erected a larger one. It was from NOF that Mr. Jenkins broadcast still photographs to Philadelphia, Boston and other cities in 1923.
To illustrate motion, a small model Dutch windmill was erected and the blades propelled slowly by wind from an electric fan. The image of this was through a lens onto a ground glass. From this ground glass the image was picked up by Mr Jenkins apparatus in much the same fashion that it is for a still photograph. That is, a small sensitive pencil travels across it making approximately fifteen lines to the inch, converting the light intensity into electrical intensity or electrical modulations.
These modulations were broadcast over a wavelength of 546 meters and picked up in Mr Jenkins Connecticut Avenue laboratory. Here the modulations were converted back into light values, and a pencil of light made to travel in the same fashion as the sending... [here the clipping ended].
[Jenkins had claimed to have transmitted a moving image as early as 1923. Baird's first public demonstration was 25th March 1925. Whoever did what first, these two experimenters were both working at almost the same time on mechanical television- a short lived cul de sac quickly replaced by electronic television]
"To consider the development of Television and to advise the Postmaster-General on the relative merits of the several systems and on the conditions under which any public service of Television should be provided."
The report naturally goes into a good deal of detail which it is scarcely necessary to include in a summary here. There are, however, several points of outstanding interest contained in thereport which will be briefly referred to.
The Committee makes it clear that the present 30-line broadcast television system is not suitable for a regular public service, although it is acknowledged that it has served a useful purpose so far. The recommendation is therefore made that the existing low-definition broadcast should be maintained if practicable for the present but that it might reasonably be discontinued as soon as the first station of a high-definition service is working. It should then be a matter for an Advisory Committee, which it recommends should be set up to guide the development of television broadcasts in the early stages, to recommend whether or not low-definition broadcasting should continue in addition.
High-quality Transmissions
It had been generally supposed that 180 lines might be recommended as a starting-off point for the new service. It is interesting, therefore, to find that the Committee recommends that a beginning should be made with 240 lines per picture, with a minimum picture frequency of 25 per second, and that the possible use of an even higher order of dennition and a frequency of 50 pictures per second is not excluded. It is stated that the price of receivers to the public is expected to be between GBP 50 and GBP 80 at the start, although when receivers are made on a large scale under competitive conditions this price may be expected to come down substantially.
The Committee has been quite definite on the point that the proper authority to undertake the transmissions should be the B.B.C., giving as one reason the fact that sound is an essential adjunct to television and that sound broadcasting is already a B.B.C. monopoly. It is, however, stated that whilst it is thought that the British Broadcasting Corporation should exercise control of the actual operation of the television service to the same extent and subject to the same broad principles as in the case of sound broadcasting, the initiation and early development of this service should be planned and guided by an Advisory Committee, to be appointed by the Postmaster-General. Since the report appeared, the Postmaster- General has appointed such a committee, which is to be composed as follows:-
Lord Selsdon (chairman).
Sir Frank Smith, secretary of the Department of Scientific and Industrial Research (chairman of a technical sub-committee).
Col. Angwin, Assistant Engineer-in-Chief of the Post Office.
Mr. N. Ashbridge, Chief Engineer of the B.B.C.
Vice-Admiral Sir Charles Carpendale, Controller of the B.B.C., and
Mr. F. W. Phillips, Assistant Secretary of the Post Office.
Secretary, Mr. J. Varley Roberts, of the Post Office.
The report explains the necessity for the use of ultra-short waves for high-definition transmissions, and points out that at present there should be no difficulty in the choice of suitable wavelengths in the spectrum between 3 and 10 metres for public television, although in allocating such wavelengths regard must be paid to the claims of other services.
Limitations of Range
The transmitting stations should be situated at elevated points, and it is mentioned that the mast at present used in Berlin is about 430 feet high, and the question of employing masts of even greater height is under discussion in Germany.
It is stated that experience both here and abroad seems to indicate that these ultra-short waves cannot be relied on to be effective for a broadcast service much beyond what is commonly called "optical range." Generally speaking, it is at present assumed that the area capable of being effectively covered by ultra-short-wave stations is a radius of approximately 25 miles, whilst in hilly districts this may be considerably reduced. But, nevertheless, it is thought that with the erection of ten stations it should be possible to provide a service for 50 per cent. of the population.
The Committee is quite emphatic in recommending the P.M.G. that there should be no delay in starting a service, and that at first a station should be set up in London, and other stations as quickly as possible thereafter, each new station to take advantage, as far as possible, of any new developments which may take place in the mean time. Having examined the systems of all those who were prepared to demonstrate, the Committee recommands that in the first instance the Baird system and the Marconi-E.M.I. system should both be set up to operate a London transmitter alternately, and that the nature of the transmissions should be such that the same receiving equipment should be suitable for the reception of both with minor, if any, adjustments.
No Receiver Monopoly
The Committee considered that the establishment of a Patent Pool which would include all television patents, so that the operating authority could be free to select from this Pool whatever patents it was desired to use for transmission, would be the ideal solution, but the Committee explain that they were compelled to abandon the idea that the formation of a comprehensive patent Pool should be a condition precedent to the establishment of a public service, although they maintain that in the interest of the trade itself and the public such a Pool should be formed. They express the hope that events will shape themselves in such a way as to lead to the formation of a satisfactory Patent Pool at no distant date.
Having agreed that the Baird Company and the Marconi-E.M.I Company should both be given the opportunity of supplying apparatus for the London station, it is recommended that besides any other con ditions imposed, acceptance of offers should be subject, in each case, to the following conditions precedent :-
(a) The price demanded should not, in the opinion of the Advisory Committee, be unreasonable .
(b) The British Broadcasting Corporation to be indemnified against any claim for infringement of patents.
(c) The Company to undertake to grant a licence to any responsible manufacturer to use its existing patents, or any patents here-after held by it, for the manufacture of television receiving sets in this country on payment of royalty.
(d) The terms of a standard form of such licence to be agreed upon by the Company with the Radio Manufacturers' Association, or, in default of agreement, to be settled in accordance with the provisions of the Arbitration Acts, 1889 to 1934, or any statutory modification thereof, either by a single arbiter agreed upon by the Company and the Radio Manufacturers' Association, or failing such agreément, by two arbiters- each of the parties nominating one- and an umpire nominated by the Postmaster- General.
(e) The Company to agree to allow the introduction into its apparatus at the stations of devices other than those claimed to be covered under its own patents, in the event of such introduction being recommended by the Advisory Committee.
(f) Transmissions from both sets of apparatus should be capable of reception by the same type of receiver without complicated or expensive readjustment.
(g) The definition should not be inferior to a standard of 240 lines and 25 pictures per second.
(h) The general design of the apparatus should be such as to satisfy the Advisory Committee, and when it has been installed tests should be given to the satisfaction of the Committee.
The Committee recognises that in the development of the service constant change, at least in detail, may be necessary as improvements are made, and they point out that a more difficult situation will arise if a completely new system, requiring a new type of receiving set, should be evolved. It is suggested that no drastic change in the system, necessitating a change in receivers, should be made without reasonable notice being given by the B.B.C., and that in the initial stages this notice should not be less than, say, two years.
The report discusses the finance side of the problem and recommends that there should be no special television licence, nor any increase in the present amount of the broadcast receiving licence, but that the revenue from this licence should, for the present at least, meet the requirements of the television service.
The report concludes with the Committee's hope that every encouragement will be given to experiment and research in television, both by firms and by private persons, indicating that in their view the establishment of a broadcast television service should not interfere with the granting of licences by the Postmaster-General for experimental transmissions in addition to the regular service suggested by the Committee in its Report.
SO far so good. Now that the first excitement of the publication of the report of the Television Committee has died down, it may be of interest to consider what effect it may be expected to have in bringing about a broadcast service of television of high definition.
The Television Committee has carried out an extremely diffcult task with most commendable thoroughness. The report is not only an unbiased estimate of the present stage of development of television, but it has the merit, in addition, of being frank in its recognition of some of the difficulties.
It has certainly come to us as a surprise that the Committee recommended that the degree of definition at the outset should correspond to 240 lines with a minimum picture frequency of 25 per second. This is indeed a high standard to demand of the service in its initial stages, but if the Committee are satisfied that it can be satisfactorily carried out we can only commend their enterprise in not being content with less.
The report states that it is undesirable to abandon the present facilities of 30-line transmissions until "at least a proportion" of the observers have the opportunity of receiving a high-definition service, and they therefore recommend that the low-definition broadcasts might reasonably be dis continued "as soon as the first station of a high-definition service is working." The cost of maintaining a 30-line transmission must, of course, be taken into account, but it seems to us rather unsatisfactory that these transmissions at present receivable over a wide area should be discontinued because a higher definition service is working for the benefit of those in the London area.
It depends largely, of course, on how many observers of the present 30-line transmissions there are beyond the probable range of the high-deflnition service in London.
On the question of patents we are sorry that the Committee did not find it possible to take a firmer line. In the report they state that they have seriously considered whether they should advise the Postmaster-General to refuse to authorise the establishment of a public service of high-definition television until a comprehensive Patent Pool had been formed on terms considered satisfactory by the Advisory Committee. They explain that they came to the conclusion that the formation of such a Pool at an early stage would present extreme difficulty.
The Real Problem
It is only natural that the publication of this report should have awakened a great deal of interest in television, if only on account of the amazing scientific achievement which it represents. There seems to have been created, however, an idea that the Committees report actually heralds a television service as essential to sound broadcasting as sound now is to the film. Such a view is, we think, premature.
When the first high-definition station is set up in London what, in fact, we shall have is a service which is an improvement upon the present experimental television broadcasts in so far as the pictures will show very much greater detail, and the broadcasts will be more frequent. Before the public is likely to maintain enthusiasm for television something more than this must be achieved. The greatest problem of television has yet to be solved, and this in our opinion, is devising programme material rather than over- coming technical difficulties.
See also Post Office Statement 14/6/1935
IMMEDIATELY the B.B.C. begins broadcasting high definition television, Electric and Musical Industries, it is stated, will be ready to market television receiving sets. Although it is too early to say what the price of these sets will be, the Company believes that the price mentioned in the committees report, viz., GBP 50 to GBP 80, will be more or less correct.
"We quite agree," continues the E.M.I. statement, "that radio sound broadcasting will still, for many a year to come, dominate the B.B.C. prograimmes. Moreover, we do not believe that television will in any way interfere with developments in radio sound broadcasting, with its ever increasing entertainment value. Therefore our company, as well as all other manufacturers in the radio industry, are going right ahead with the development of the manufacture and sale of radio sets for sound."
[Historic Note: High definition Public tv broadcasts in Britain began 26th August 1936 with alternating systems- one day a 240 line Baird system, the next day the EMI-Marconi 405 line system (including 28 unused lines). A regular service commenced 2nd November 1936 with the systems alternating each week. On the first day the broadcast was from 3pm to 4pm and then from 9pm to 10pm. On 30th November 1936 the Crystal Palace burned to the ground, destroying much of Baird's equipment (The transmitting equipment was at Alexandra Palace.) In February 1937 the 405 line system was left on its own in the UK. In 1948 France broadcast using 819 lines. Elsewhere in Europe a small change to the American 525 line standard produced 625 lines (including 49 blank lines, later used to carry program and Teletext data). The BBC continued to broadcast mono 405 lines until 1985 although 625 line broadcasts commenced in 1964.]
SIR KINGSLEY WOOD infused a rare sort of expectancy among the party of hard-boiled journalists who met in an House of Commons Committee Room last week. The excitement was natural, for the subject of television is outside the Pressman's usual range of topics.
When, with pardonable pride, the P.M.G. had made his statement on the findings of the Television Committee, he invited questions. One could tell from the questions that television is still suspect. No one really knows where it may end, and though Sir Kingsley raised a laugh, it was well that he did say that the art does not confer the ability to look into other people's houses.
New High Frequency Cable
One of the more important announcements was that a special new Post Office cable would permit the transmission of sufficiently high frequencies to link up the various ultrashortwave stations which will eventually comprise the television chain.
The Provincial Transmitters
No decision has been taken rcgarding the position of the provincial stations which will follow the initial experiments in London, but we may assume without doubt that all the natural vantage points in the neighbourhood of large cities will be utilised. Height is the first essential.
The 30-line Tests
It is gratifying to know that 30-line experimenters are not to be left in the lurch. The Baird process tests from Broadcasting House will definitely continue until the hoary pioneers of to-day have a chance to acquire more ambitious gear.
The Pioneer Television Producer
When high-definition television tests really get going I hope that we shall not forget the pioneer work of Eustace Robb, who has done miracles with the material at his disposal in providing programmes of real entertainment value on the 30-line system.
Mr. Robb's Future
The list of artists who have built up these television programmes includes some of the most famous in this or in any other country; and the fact that they were induced to make appearances in the flickering 30-line scanning beam must be largely ascribed to the vigour and optimistic outlook of Mr. Robb.
If he could make such a success of low-definition television, what could he not do with 240-line scanning and a larger picture?
When We Look
By the way, the man at the reeeiving end at last has an official designation. On page 22 of the Television Committee's report, reference is made to a "television looker's licence." As Sir Walford Davies will say: "Good evening, television lookers all!"
THE members of the Television Advisory Committee appointed to recommend a suitable site for the B.B.C.'s first official television transmitter have visited the Alexandra Palace to consider the advantages of that position for the installation of equipment to supply London and the Home Counties with sound and vision programmes.
One of North London's most prominent buildings, the Alexandra Palace has much to recommend its choice. Situated on a hill rising 324ft. above sea-level, the Palace buildings, which date from 1875 and cover nearly eight acres, have a tower at each of four corners rising a further 145ft. By making full use of any of these towers, which also contain ample accommodation for the necessary studio and equipment rooms, an effective height of nearly 470ft. is available for the erection of aerials without any additional structures.
From the expanse of country visible on a clear day the "optical range" of an ultra-short-wave transmitter should be considerable, the red light at the end of Southend pier, about 36 miles away, being discernible at night.
If the television station does find its home at Alexandra Palace it will not bc alonc in the supply of public entertainment catered for under this roof, where a theatre, concert and exhibition halls, ball room and skating rink are to be found.
The Grand Central Hall, with its 57,330 sq. ft. and one of the four largest grand organs in Europe, may one day earn the title of the world's largest broadcast studio. The hall has a seating capacity of 8,000.
An ideal subject for a popular type of television broadcast can be found within the boundaries of the grounds. The well- known Alexandra Park racecourse lies at the foot of the southern slopes, a vantage point from which the whole of London stretches before the eye, and the Crystal Palace, the hills of Kent and Surrey appear almost within grasp.
See also Post Office Statement - 14/6/1935
HITHERTO high-definition television tests in Germany have been confined to scientic laboratories and a few expert amateurs. To-day (Friday) a regular sight and sound service begins from the Broadcasting Tower in Berlin and all members of the public can participate.
THE ultimate aim of those responsible for broadcasting in National-Socialist Germany is to make it technically possible for every German not only to listen to the speeches of the Fuhrer but also to see him speaking. The present development of broadcasting has made the first aim possible, and now work is being speeded up to provide a suitable television service so as to realise the second.
The German Post Office laboratories started high-definition test transmissions in August, 1933. At that time 90-line pictures were broadcast. A few months later, in 1934, a second ultra-short-wave transmitter was provided and this was used for 180 line pictures, the accompanying sound being broadcast by the older transmitter.
These stations operate with a power of 16 kw, but the long feeder line up the Witzleben radio tower which supports the two dipole aerials, 430ft. above ground level, consumes a portion of this. Taking this into account and making use of the usual Copenhagen formula for calculating power of broadcasting stations, the power in the aerial can be said to be approximately 1.5 to 2 kW, a very large amount for ultra-short waves.
Thirty-Mile Range
Up to the present the reception of these test transmissions, which have taken place for several hours every day, has been limited to scientific laboratories and to those television amateurs capable of building their own ultra-short-wave receivers and of handling the high voltages required for successfully operating cathode ray tubes. The Post Office engineers broadcast strips of film, and although these were often interesting there was no dehnite programme, and one could therefore not talk of entertainment value.
The German Broadcasting Company's decision to start supplying regular programmes will be welcomed by all concerned in Germany, as now the question of supply of receivers will come nearer solution. One German firm, Loewe, claim to be able to supply all-mains-operated sight and second television receivers for RM. 600. These receivers are comparatively simple to operate and have already been demonstrated in London to the Television Committee as well as in Berlin.
Another German firm, Telefunken, supply a much larger type of apparatus, although the actual picture is not very much bigger. At the present moment it is not to be expected that a large number of the German public will buy television receivers. The broadcasters, however, have ordered a certain number from both companies, and these receivers will be suitably distributed in the service area of the short-wave transmitters. Tests have proved this to be within a radius of some thirty miles from the radio tower.
The persons entrusted with looking-in will then be asked to provide constructive criticism both as to the nature of the programmes and of the actual practical working of the receivers and the entertainment value achieved.
Meanwhile the German Post Office laboratories and Telefunken are hard at work perfecting a system of electrical scanning and are also working on the problem of suitable amplitiers and cables to provide for an even higher degree of definition than the present 180 lines. In Germany it is generally accepted that 180 lines is the minimum for a television service with entertainment value.
On the other hand, the difliculties of practical high- power ultra-short- wave broadcasting with even higher definition are at present considered to be too great to warrant the further retarding of the public television service. It will be remembered that in Germany 30-line transmissions never took place on any large scale, and therefore, as far as the German general public is concerned, they are still strangers to television except for what they have seen at the various radio exhibitions.
One hundred and eighty lines and twenty-five frames per second means a frequency band of 500,000 cycles for transmission, and 240 lines would mean one million cycles. Most people realise that this is too big a jump, especially when a practical system of 180 lines actually exists and suitable receivers are available.
Television News Reels
The opening of the television service, which was first scheduled for the second week in March, has now been definitely fixed for to-day (March 22nd). Programmes will be broadcast three times a week from 8.30 p.m. to 10 p.m. CET, and will consist of excerpts from news reels and of a full entertainment film. Programmes will be changed once a week as at a cinema. Within a short while after the opening of the service the German Broadcasting Company will start providing its own news reel. A suitable sound-recording car with the necessary lighting van has already been ordered. These news reels will be taken and processed in the usual manner, and broadcast each evening under the title: "Mirror of the Day."
Apart from these ordinary news reels use will be made of the daylight television van operating on the intermediate film system to provide red- hot actuality broadcasts of important events. These will be brdadcast at the time of happening, and will then be repeated in the evening again.
The transportable twin ultra-short-wave transmitters which were ordered some months ago are now nearing completion, and it is hoped to start tests with the second set of high-power transmitters in the late spring. These transmitters are first to be tried out on the Broeken mountain, and modulation will be received from Berlin by wireless link. The transmitters themselves will all be mounted on suitable trucks for transport by road.
The opening of a public high-definition television in Germany at the present moment can be considered as a preliminary run to gather practical data on the actual service requirements, and programmes will gradually be developed from week to week. On the other hand, the laboratories will be at it full speed ahead to produce a "Volks-Fernseher" (a peop1e's television set). The quality of the pictures at present transmitted from the Berlin Broadcasting House and received on a Telefunken receiver is exceptionally good, and it was possible to look in for a full half an hour at a film and really enjoy it
Naturally 240 lines would be better, but the Gerrrians think quite rightly that for the small circle who will be able to afford relatively expensive receivers 180 lines has sufficient entertainment value. To-day the Press will be generally invited to the opening, and important pronouncements may be expected, especially as a technical German research engineer has only just returned from portant pronouncements may be expected, especially as a technical German research engineer has only just returned from America where he is said to have investigated systems of electrical scanning.
THERE is no doubt that the wide publicity television has received, which is likely to be very much more intense when the official transmissions are about to begin, will loosen the purse strings of the public, and sets for television reception will be bought in considerable numbers.
Statements have already been appearing in the Press to the effect that low-priced receivers for the reception of the present 30-line transmissions will be available very shortly and that these sets will be capable of being converted later on for the high-definition transmissions at a very small cost.
30-line v. High Definition
The construction of television receivers for the 30-line transmissions is a comparatively easy matter, but lack of public demand on account of the temporary and experimental nature of these transmissions and their poor entertainment value has limited the sale. The manufacture of high-definition receivers is a much more difficult task ; we know that the estimated cost to the public of such sets is above, rather than below, GBP 50.
It is quite a simple matter to modify a high-definition receiver to make it suitable for the reception of the present 30-line transmissions, but it is a very different problem to attempt to reverse the process.
The basic idea of producing sets for the present transmissions which can later be made equally suitable for high-definition reception is a very good one if it can be successfully carried out.
But the public must not expect that by this method it will be possible to get a satisfactory high-definition receiver at a lower cost than if the receiver had been designed in the first place for high-definition reception. The public, before buying sets of this nature, should be confident that converting the receivers can be done satisfactorily at an agreed cost, and that the concerns which sell the sets now will all be there to make the conversion when the time comes.
WE have always contended in these pages that when television reached the stage of becoming a public service all manufacturers of wireless equipment should be in a position to participate in it on an equal footing, subject to licences from owners of patents, but, although this view was strongly supported in the Television Committee's Report, in practice this ideal is not being carried out.
Nearly all British manufacturers are interesting themselves in the possibilities of television and are at least considering the advisability of producing sets for the public. But equal facilities are not available to them. In London the E.M.I.-Marconi Company and the Baird Company are carrying out test transmissions for their own benefit, to enable them to perfect their receivers, but the rest of the industry and research workers on the problem are not only unaware of the times of these transmissions, which are irregular, but they do not know the precise nature of them.
It is exceedingly difficult for those working on the design of receivers to carry on unless they have transmissions to receive and test with. It does not seem to us to be a fair arrangement for the two companies mentioned above to be alone in having facilities of this kind. It may be said that the Postmaster-General would readily grant experimental transmitting licences for television to any other firms which cared to apply for them, but this would not really meet the case, as the transmissions will ultimately be by the Baird and E.M.I.-Marconi systems and unless the designer knows exactly what is the nature of these transmissions he cannot hope to make headway in the production of receivers.
If the EMI.-Marconi Company and the Baird Company were not themselves interested in the production of television receivers in competition with other manufacturers, there would, of course, be no unfairness, but this is not the case.
We cannot imagine that it was the intention of the Television Committee or of the Postmaster-General to make these two companies a present of all the business in the sale of sets which may accrue when television transmissions start, but this is, in fact, what is being done, and it is time some action was taken to put an end to a very one-sided state of affairs.
THERE are signs that the public is now settling down to a more sober view of television after the first outburst of excitement following the publication of the Television Committee's Report to the Postmaster General. The problems involved begin to show themselves in their proper perspective and it is realised now that when the proposed station in London starts transmitting this will only be a modest beginning, and that the development of an efficient service of public interest must be a gradual process.
In an article published in the issue of The Wireless World of August 3rd last year, under the title "Financial Aspects of Television," it was brought home to us how serious an obstacle to rapid development was the probable high cost of organising a national service. It was shown that the future of television was so bound up with the financial side that the technical aspect could not properly be considered except in association with financial considerations. Elsewhere in that article the statement appeared "It does not look as if the finances of the B.B.C., on the basis of their present proportion of the licences, could stand the strain of endeavouring to provide television programmes, even if they might scrape together the cost of erecting the stations over a fairly long period of time."
Fortunately, the B.B.C. is to have some assistance on the financial side, for it has now been announced that a grant of GBP 50,000 is to be made to the B.B.C. through the Post Office estimates to aid the development of the television service. This sum should be a considerable assistance, but it looks as if an equal amount at least will have to be found from year to year for the provision of programmes alone, quite apart from the erection of stations.
On the commercial side, too, there are difficulties. Those concerns which have done most of the development work on television have already sunk large sums which have so far been unproductive of revenue, and if royalties paid to them as owners of patents by manufacturers of television receivers and profits through the sale of their own receivers are to be their only sources of revenue, it may be some time before any appreciable reward for their efforts can be garnered. In order to popularise television in this country too, manufacturers will undoubtedly endeavour to put. out sets at the lowest possible prices, thereby leaving themselves a somewhat meagre margin of profit.
Financial Risks
It would be over optimistic, too, to suggest that there is no element of risk attaching to the future success of television from the point of view of public appeal, and this, as we have pointed out before, is where the B.B.C. has had to shoulder a big responsibility. If the public has been led to expect too much of television and the scope of the programmes when they start is disappointing, then development may prove to be very slow indeed.
Meanwhile, we should do all that we can, short of raising the hopes of the public too high, to support the B.B.C. in their effort, as well as giving encouragement to those pioneer companies who have invested so much capital in the enterprise and who merit a full reward for their efforts and for the risks which they have been prepared to take.
Premature Standardisation would Freeze the Art
By A. DINSDALE
AFTER having been "just around the corner" for a number of years, American television has at last reached the corner and decided to take a peep around it and see if, it is safe to come out into the open. According to an announcement made by David Sarnoff, president of the Radio Corporation of America (RCA), at the annual meeting of shareholders held May 7th, television is to be taken out of the laboratory for field tests.
At first glance it may appear that America is anxious to catch up with Great Britain and Germany, but there is probably an element of commercial rivalry as well. R.C.A. has for years been developing the television system of Dr. Vladimir K. Zworykin, while the Philco Radio and Television Corporation has been sponsoring the system of Philo T. Farnsworth.
Both systems would appear to be at about the same stage of development, so that whoever breaks into the commercial market tirst stands to win an advantageous position.
Mr. Sarnoff estimated that the campaign to introduce television commercially will cost one million dollars, and that between twelve and fifteen months will be required to prepare blue prints and complete installations. A start will be made in New York, using the Empire State building as the ultra-short-wave transmitting station. Experimental transmissions have been made between this building (the extreme top of which is 1,250ft. high) and the R.C.A. laboratories in Camden, N.J., ever since the Empire State building was completed nearly four years ago. Using a wavelength of approximately 6 metres, a range of about twenty-five miles is expected. This will cover centres of population aggregating something like twenty million people.
The second step in the programme will be the manufacture of a limited number of image receivers, which will be distributed among strategic points.
The third step will be the development of an experimental programme service to determine the most acceptable form of television entertainment.
R.C.A. Views
"Let me emphasise," said Mr. Sarnoff, "that, while television promises to supplement the present service of broadcasting by adding sight to sound, it will not supplant or diminish the importance and usefulness of sound broadcasting.
"In the sense that the laboratory has supplied us with the basic means of lifting the curtain of space from scenes and activities at a distance, it may be said that television is here. But as a system of sight transmission and reception, comparable in coverage and service to the present nationwide system of sound broadcasting, television is not here, nor around the corner. The all-important step that must now be taken is to bring the research results of the scientists out of the laboratory and into the field.” Mr. Sarnoff also said :
"Important as it is from the stand-point of public policy to develop a system of television communication whereby a single event, programme, or pronouncement of national interest may be broadcast by sight and sound to the country as a whole, premature standardisation would freeze the art."
With New York as a nucleus, it is probable that, in time, other transmitting stations will be built which may be connected to the New York station either by wire or by wireless. The existing telephone lines, of course, cannot handle the frequencies involved, and the new hollow conductor type of high-frequency "cable" recently announced by the Bell Telephone Laboratories, while apparently satisfactory for the purpose, is extremely expensive and will take a long time to install in any extensive network form. For this reason, experiments are being made to determine the feasibility of relaying television programmes by means of ultra-short wave wireless relay transmitters.
Does America Lead?
Mr. Sarnoff declared that the United States is further advanced in television than any other country, but admitted that many technical problems remain to be solved before the television broadcasting as a public service can be offered even over a limited territory. As to the present status of the art, Mr. Sarnoff explained that the degree of detail obtainable "is somewhat comparable in its limitations to what one sees of a parade from the window of an office building or at a world series baseball game from a nearby roof or of a championship prize-flight from the outermost seats of a great arena."
If this is the best that American television has to offer, and if America is really farther advanced than any other country, then the prospects of television, as entertainment, do not appear to be over-bright at present. However, a start must be made sometime, and it may be argued that broadcasting, as entertainment, was not so hot when that art was first introduced to the public. On the other hand, general technological development has progressed so far in the meantime that the public is now much more critical, and may not take kindly to a view of the Cup Final "from a nearby roof."
However, Mr. Sarnoff is at least maintaining his reputation for enterprise, and is to be congratulated on his bold step, which somebody had to be the first to take in the United States sooner or later.
30 line Baird Process Transmissions, vision 261.1m, sound 292.2m
Monday 10th June 11.15pm to midnight:
Items from "Let's go gay". John Hendrick and John Rorke in songs; Freddie Carpenter with Jessie Blane in feature dances; Jane Carr and Charlotte Leigh in songs; Elinor Shan in mimes and dances; Sydney Jerome's Quintet.
Wednesday 12th June 11.15pm to midnight:
Programme of folk songs and dances from India, Ceylon and Tibet. Surya Sen, the Sinhalese singer, assisted by Nelum Devi.
[History Note: The 30 lines tv transmisions ceased September 1935]
THE Postmaster-General announces that he has received a communication from the Television Advisory Committee regarding the choice of a site for the projected London Television Station and other matters relative to the proposed experimental television service.
Atter having carefully considered a number of possible sites, the Committee have recommended the adoption of the Alexandra Palace for the station. This recommendation has been approved by the Postmaster-General; and the British Broadcasting Corporation have made arrangements with the Alexandra Palace Trustees for the use of a portion of the Palace buildings for the station.
The ground at the Alexandra Palace is 306ft. above sea-leve1; and it is proposed to erect a 300ft. mast on the site, thus providing an aerial height of 606ft. above sea-level, which, it is considered, should enable a high-definition television service to be provided for the London area.
As recommended in the Television Com mittee's Report, the Baird Television Company and the Marconi-E.M.I Television Company are being invited to tender for the supply of the necessary apparatus for the operation of their respective systems at the London station.
The Baird Company propose for their system the adoption of a standard of picture definition of 240 lines sequential scanning, 25 picture traversals per second, 25 complete frames per second; and the Marconi-E.M.I. Company propose for their system a standard of 405 lines, 25 pictures per second, interlaced to give 50 frames per second, each of 202.5 lines.
Subject to satisfactory tenders being received, the Advisory Committee recommend the adoption of these standards for a public service during the trial period. Whilst it is contemplated that each system will be operated mainly on the standard proposed for it by the relative company, the alternative standard may be employed by permission of the Advisory Committee with either system. In such event due public notice would be given of the change.
The Committee have satisfied themselves that receivers can be constructed capable of receiving both sets of transmissions without unduly complicated or expensive adjust ment.
The Committee propose that the vision signals should be radiated on a wavelength of about 6.6 metres, and the associated sound signals on a, wavelength of about 7.2 metres.
If the tenders submitted by the two companies are accepted, such technical information regarding the characteristics of the television signals radiated by the two systems as will facilitate the designing of television receivers capable of picking up those signals will be made available to manufacturers by the respective companies.
THE Television Committee of the Federal Communications Commission has recommended that television stations should be permitted to broadcast a limited proportion of commercial programmes.
Whilst the Committee hold that television is still highly experimental, the members feel that it has reached a crucial stage, but extensive developments are yet to be accomplished before television receivers can be bought with the same assurances that go with the sale of an ordinary receiving set.
Fewer than 1,000 receivers have been sold since May, 1939, when the N.B.C.'s New York station started regular transmissions.
It is announced in Broadcasting that the Committee has recommended the allocation of three channels to metropolitan districts with a population of over 1,000,000; two channels to those with a population between 500,000 and 1,000,000, and one channel to districts with fewer than 500,000 inhabitants. With this assignment of frequencies a maximum power of 10 kW is stipulated.
Referring to the cessation of television development abroad the report states: An opportunity exists for American industry to construct foundations for a position in the world television market of the future by undertaking active steps at this time to further the technical and operating development of television in this country. This opportunity should not be lost.
As is already known, transmissions from the London television station ceased on September 1st, for reasons of national defence.
Mr. Sagall; managing director of Scophony Ltd., has submitted a memorandum to the Postmaster-General and the Television Advisory Committee urging them to consider the question of restarting television transmissions. He says:
If the objections of the Defence Authorities to the transmissions of television by radio are incontrovertible, the possibility of introducing television over wires, i.e., over telephone lines or their equivalent, should now be carefully considered by the Government Departments in conjunction with representative television interests.
Mr. Sagall points out thata wired television system would be the ideal method of making television accessible to the bulk of the population, for in its wake would come a rental system of television sets, and a charge of 5s. (25p) a week is suggested. The suggestion is that the rent should include a contribution towards the provision of programmes.
Transmission by wire would not, of course, be subject to atmospheric and electrical interference.
THE controversy arising out of the announcement of the Federal Communications Commission suspending its concession permitting "limited commercial" operation ot television transmitters from September 1st, culminated in a statement by President Roosevelt in which he advocated a free, competitive television industry on the lines of present-day sound broadcasting in the States.
"The F.C.C. and the industry," says a writer in Broadcasting, "were placed under a virtual mandate from the Senate Interstate Commerce Committee to get together quickly and stop what has been termed the bickering and bungling that are delaying television development."
The question of standardisation of transmitting systems is the crux of the television situation in the States.
R.C.A.-N.B.C. has a 441-line system, whilst the recently licensed DuMont transmitter employs 625 lines.
Philco's vertical-polarisation 605-line system has, however, been dropped, and the American R.M.A. 441-line standard adopted.
Peter Carl Goldmark (Hungarian: Goldmark Peter Karoly) (December 2, 1906 - December 7, 1977)
He was instrumental in developing the long-playing microgroove 33-1/3 rpm phonograph disc, the standard for incorporating multiple or lengthy recorded works on a single disc.
Goldmark developed field-sequential color technology for colour television while at CBS. The system, first demonstrated on August 29, 1940, and shown to the press on September 3 used a rapidly rotating color wheel that alternated transmission in red, green and blue. The system transmitted on 343 lines, about 100 less than a black and white set, and at a different field scan rate, and thus was incompatible with television sets currently on the market without an adapter.
Goldmark was aware of and inspired by the somewhat different 1928 Baird colour tv experiments.
Although CBS did broadcast in colour with the Goldmark system in 1950-1951, the "compatible color" technology developed for RCA and NBC (by a team led by Richard Kell, George H. Brown and others) was compatible with existing black and white TVs. Goldmark and others have pointed out that the CBS colour wheel system did provide better picture quality (although lower image resolution) than RCA's system, but the compatibility problem proved its downfall. An improved RCA/NBC color system submitted in July 1953 became the industry standard chosen by the Federal Communications Commission (FCC) in December 1953. Ironically, cameras using the color wheel system continued to be used for scientific research for several more decades, including the color lunar surface TV cameras during all the 1970s NASA Apollo moon landings (watch for colour fringing on moving edges).
The colour photo alongside is said to be an off screen shot of a colour tv transmission of a surgical operation, indicating the early quality of the CBS system.
In 1953 Peter Goldmark embarked on simplifying the color tube used in the RCA developed system, and with help from his CBS staff developed a way to photoengrave the color dots right on the faceplate of the tube. This was such a breakthrough that RCA stopped their research on their next generation tube and took out a license on the CBS patent.
NOW for the contempory report, from a British magazine of November 1940:
Colour Television in U.S.A.- The Columbia System Described
By A. Dinsdale.
As recently reported, television in the United States was thrown into an uproar by bureaucratic ukase early this spring. Recriminations, charges and counter-charges were defiantly hurled about by the various protagonists. But it was no use. When the noise of battle died, television in the United States was dead, too, deader than a doornail- at least for the time being. Transmitters went off the air to be rebuilt to operate on higher frequencies. Nothing seemed to disturb the autumnal calm until suddenly, like a bolt out of the blue, the Columbia Broadcasting System put on a demonstration of television in full colour!
True, the subject matter was provided by coloured film run through a film scanner, and not a direct pickup. Nevertheless the demonstration was a very good one, highly convincing, and most interesting in its implications.
For a long time many people have wondered just what C.B.S.was up to. It may be remembered that in 1931 and 1932 C.B.S transmitted television programmes by the mechanical disc method, These programmes were discontinued and C.B.S. apparently lost interest in television until 1936, when Dr. Peter Goldmark, formerly with Pye Radio, Ltd., was appointed television chief engineer. About two years ago Dr. Goldmark built a high-power vision transmitter on top of the tower of the Chrysler Building in New York, and it was announced that C.B.S., would shortly recommence the broadcasting of television programmes in competition with N.B.C. But. nothing happened, The transmitter seemed to be on the air only at rare intervals, and then only to transmit test patterns.
Dr. Goldmark says he has been working on colour for some time. but very intensively only during the past six months. Asked how he came to be interested in colour television he explained that he is an enthusiastic amateur motion picture photographer. He began to use colour film, and thereafter acquired what he described as an inferiority complex not only towards b1ack and white film but also towards black and white television.
In the demonstration given in New York last September 4th, transmitter and receivers were connected by cables, but in a private demonstration given a week previously to James L. Fly, Chairman of the Federal Communications Commission, the images were broadcast by radio from the Chrysler Building transmitter. This transmitter was then immediately dismantled to make the change-over to its new frequency allocation.
The film used for the demonstration was 16 mm. Kodachrome, and included a wide range of subjects, closeups and long shots. In one scene a girl in a brightly coloured dress held up a large black-and-white photograph, of herself. It speaks well of both the Kodachrome process and the television process that this photograph showed up black-and-white on the television screen.
A most interesting basis of comparison was provided by C.B.S. engineers. Alongside the colour television receiver they placed an ordinary black-and-white receiver, and fed it from the same signal scource. It was thus possible to make comparisons between the black-and-white image and the coloured image. The black-and-white image provided slightly better detail than the coloured image, and by comparison with customary black-and-white television the image was much less "contrasty." The effect is best compared with the difference between ordinary 16 mm. film and panchromatic film.
The colour image was steady, the colours perfectly registered. In fact, it was difficult to realise that one was not watching a Kodachrome film on a home movie screen. As to the improvement lent by the addition of colour the additional value is ex- actly the same as in the case of the addition of colour to the ordinary home movies.
Only a limited amount of technical information was released; Dr. Goldmark pleaded the patent situation, the fact that C.B.S. is not interested in manufacture, and that they wish to make their revelations first to the National Television Committee. This latter event is expected to occur about January 1st next, by which time C.B.S. hopes to have its radio transmitter rebuilt and operating again.
Frame Periodicity
The film used in the demonstration was originally shot at 64 frames per second, and run through the television scanner at 60 frames per second, instead of the usual 24 frames per second. Work is now proceeding on a film scanner which will use 16 mm. film shot and scanned at 24 frames per second. After this has been completed, 35 mm. equipment will be built.
In contrast to the American standard of 441 lines for black-and-white Dr. Goldmark at present uses 343 lines, interlaced. He thinks he can increase the number of lines to more than 400 without exceeding the permitted 6 Mc/s band width of the. radio channel. His present equipment utilises 4.25 Mc/s of the band.
Between the film scanner and the electronic pick-up tube there is a rotating disc containing red, green and blue filters in that order. When the red filter is in front of the tube only those parts of the picture which contain red make any impression on the pick-up tube. When the green filter is in front of the tube, only those parts of the picture which contain green (and this includes yellow) register on the tube. Similarly with the blue filter. The three filters are balanced to give the effect of pure white when the picture is white, in accordance with the physical laws governing these three primary colours of light.
In front of the receiver tube is a similar rotating filter disc, exactly synchronised with the transmitter disc by means of special synchronising impulses sent out by the transmitter.
Scanning in Colour
In black and white systems, the image is completely scanned every 1/24th of a second. In the C.B.S. colour system the image is completely scanned every 1/60th of a second. However, at the end of the first sixtieth of a second only two colours have been used. The third colour requires an additional 1/120th of a second. Thus, the total elapsed time for one picture, totally scanned in full colour, is 1/40th of a second. The exact scanning sequence is as follows:-
The odd number lines are scanned in red in 1/120th of a second. The even number lines are scanned in green in 1/120th of a second.
At this point the whole picture has been scanned, but there is as yet no blue in the picture. Elapsed time: 1 /60th sec.
Now the red on the odd number lines has faded and these same lines are scanned in blue in 1/120th sec.
At this point the who1e picture has been scanned one and a half times, but in full colour on1y once, Elapsed time: 1/40th sec.
Now the green on the even number lines has faded and these same lines are scanned in red in 1/120th sec.
At this point the whole picture has been scanned twice, but in full colour only one and one third times. Elapsed time: 1/30th sec.
Now the blue on the odd number lines has faded and these same lines are scanned in green in 1/120th sec.
Elapsed time: 5/ 120th sec
Now the red on the even number lines has faded and these same lines are scanned in blue in 1 / 120th sec.
At this point the whole picture has been scanned three times and in full colour twice. Elapsed time: 1/20th sec.
And now the whole progressive cycle begins again with the odd number lines being scanned in red.
The output of the pick-up tube
with the different colour impulses unsegregated, proceeds along a single channel to the main control panel. Here the different colour impulses are sorted out and routed into three separate channels for control purposes. After passing the controls, the three sets of impulses are again recombined in a single channel and sent to the radio transmitter to be broadcast. At the receiver the impulses are not segregated, but fed directly to the electron tube.
At the main control panel each colour can be separately regulated by means of a gain control in each of the three colour circuits (after segregation). By this means an accurate colour balance can be achieved. During the demonstration, at a moment when a close-up of a large red zinnia with green leaves was on the screen against a deep blue sky, Dr. Goldmark slowly took out the red component entirely, leaving the red petals of the flower as a nondescript shadow on the screen.
Viewing in Bright Light
At one point during the demonstration the lights in the room were switched on. The image in the black-and-white receiver faded out until only the highlights were visible. The coloured image, however, held its brilliance and clarity, both in the highlights and in the shadows. In fact, it looked the same as it did when the lights were off. The only noticeable difference was a relief from eye strain when the room lights were on. This may be an item of considerable social and other significance if and when television in full colour is fully adopted and running on a daily schedule like sound broadcasting is to-day.
Both the receivers used in the demonstration were equipped with 9in. tubes.
Dr. Goldmark stated that he is working now on equipment for direct pick-ups in full colour. The only reason he demonstrated with film first, he said, was that he has been held up for some months awaiting delivery by a manufacturer of an important component part. He further stated that he estimated that direct pick-ups in colour will require two to three times as much light as is required for direct television pick-ups in black-and-white. He expects to have his direct pick-up equipment ready for operation by January 1st next.
When asked if he had to develop a composite screen of several different photoelectric materials for his pick-up tube, Dr. Goldmark replied that he found that ordinary caesium tubes were adequate to cover the entire colour range.
In reply to a further question, Dr. Goldmark stated that there is no special significance in the scanning standards he had adopted. His choices were governed entirely by considerations of convenience in relation to the equipment he had on hand, or had to build.
On the ground that C.B.S. is not a manufacturing company, Dr. Goldmark refused to be specific when asked about the cost of adding colour to existing television receiver designs. He thought the additions necessary to enable a receiver to reproduce colour might add about 10 per cent. to the list price. As to the possibility of adapting existing receivers, it depended upon their design whether they could be readily adapted. In some cases the cabinet size or arrangement would make adaptation rather difficult and expensive.
However, the receiver would still be capable of receiving his colour transmissions, but it would reproduce them in black and white, and, as already noted, the detail would be better and much less contrasty, so present owners of televisors stand to gain anyway. The necessary changes involve circuit changes to conform to his scanning standards, and the addition of a colour disc, complete with driving motor and synchronising mechanism. The diameter of, the colour disc is not quite twice the diameter of the electron tube.
Back in 1928, when John L. Baird first demonstrated a crude form of colour television, it was thought that the only way to accomplish the feat would be to use three channels, one for each colour, or else use one channel of three times the band width required for black-and-white television. Baird used the latter method. In this present day of high-quality black-and-white television, Dr. Goldmark has shown that the already overworked latitude of persistence of vision can apparently be stretched still further to provide high-quality colour television without taking up any more room in the ether than is required for the transmission of black-and-white images.
The question in the United States, as regards television in general and Government interference with it, is: And now-what next?