December 14, 1922

December 14, 1922

December 14, 1922

December 14, 1922

December 14, 1922

December 14, 1922

December 14, 2022 was the exact 100th anniversary of Ted Case’s discovery of the AEO light.

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 Just over 100 years ago, Ted Case and Earl Sponable stumbled upon the first essential piece in the eventual Movietone sound on film system, which would be the first to make audiences and the press acknowledge the dawning of “Talkies.” According to Case’s laboratory notebook that day, and in a soon to follow legal affidavit, he clearly details his fascination with the projection of a barely visible soundtrack onto a film strip using a specialized bulb using Argon gas to record the simple word “hello.” The results of the experiment were so impressive that Case immediately sought legal counsel before contacting his business partner, Lee de Forest. This day would mark the dawning of a new era in technology, placing a former greenhouse in an Auburn backyard at the center of the film industry for nearly a decade.

Excerpt from Lab Notebook , December 14, 1922

Following the experiments made on November 27 the various pieces of film mentioned were carefully examined to determine the cause of the noises heard. Examination of these pieces of film under the low power of the microscope showed that the film base material contained a large number of black specks. These specks may have been dust or dirt which was in the base when it was manufactured. They were however very small and it is thought that they were not the cause of the noises heard. When a  piece of film was held up in front of the eye against a dark background and the eye focused upon the surface of the film; if the film was now slowly moved distinct waves in the surface of the film could be noticed. These waves were present both in moving picture film and also the clear film base used in making Kodak films. It seems reasonable that these waves in the film base may be the cause of the noises heard as they would probably have a considerable distorting effect upon the light coming through the slit. Some film base was ordered directly from Eastman’s with the specifications that it come from the first step in manufacture that is before it had been run through the rolls or punches. This material has been received but has not yet been tried in comparison with the ordinary moving picture film base. 

The wave effect is visible upon its surface and it also showed the black spots when viewed under the low power of the microscope. A comparison between ordinary motion picture film base and the film base in Kodak film showed that the Kodak film base was much more noisey than the moving picture film base. This was contrary to what one would expect as the Kodak film base was about half the thickness of the moving picture film base and also contained less black specks when viewed under the microscope than did the moving picture film base. Dr. Mees of the Eastman Kodak Co. said that the same material was used in making the base for both films. 

For use in working with these moving picture films, a camera described in the notes of November 27 was made up. It consisted of two solid wood drums over which the film could be placed and arranged with a crank so that the film could be passed before a slit. For the slit, a variable slit about one-half inch wide was obtained out of an old spectroscope.

In view of the fact that we had obtained a good voice transmission with a special oxy-acetylene manometric burner, it was decided to photograph the variations from this burner upon a strip of moving picture film. A strip of unexposed film about seven feet long was mounted in the camera. The slit was adjusted to a very narrow width and a picture of the varying flame was taken. The flame was placed just outside the camera and about three inches from the slit. The film was turned past the slit by hand at the speed of about one foot per second. During the taking of thai picture the flame was made to vary by talking into the diaphragm. The film was developed; the exposure proved to be very nearly correct. The voice variations however were very small as there was too much continuous light and not sufficient amplitude of variation.

As this time Dr. Lee DeForest reported to Mr. Case that he had been using small flashlight bulbs for taking pictures of voice variations. To obtain satisfactory results, it was necessary to burn these bulbs very bright, consequently they burned out. Mr. Case had suggested to him several weeks before that he try hydrogen in his small light so that the filament would cool quicker. Dr. DeForest had evidently been thinking this over and on December 12, he requested Mr. Case to fill some of these small lamps for him with hydrogen gas. He desired the filaments to be straight and about one-eighth inches long. A number of flashlight bulbs were obtained and a suitable system set up to fill these bulbs with hydrogen gas. Two or three of these bulbs were sent to DeForest and a few kept here for experiments at this laboratory. Some pictures were taken to the variations produced in the filament of one of these little hydrogen filled bulbs. The bulb was lighted by means of a six volt storage battery potentiometer arrangement and burned to a point where the filament was a bright orange. The voice variations were then impressed upon the filament light taken directly from a four stage amplifier system. A small Federal microphone supplied the variations to the first bulb of this system. The were then amplified by a western Electric loud speaker and the output impressed upon the filament of the small bulb by means of a step-down transformer. The transformer was in series with the flashlight bulb and the storage battery or potentiometer. When one spoke into the microphone, fluctuations in the light from the flashlight bulb were noted. A number of pictures were taken of variations produced in this small flashlight bulb. 

A number of experiments were made to get the exposure correct. In most cases the photographs obtained showed as before too much continuous light and not much amplitude of variation. It was thought that the filament in these bulbs was too large and was not responding sufficiently to the impressed voice variations. Some surgical lamps were obtained from the Welch-Allyn company of this city. These were very much smaller and in fact were stated to be the smallest lamps manufactured. Two of the smaller lamps gave very good response to the voice variation. The variations could be reproduced quite perfectly by allowing the light to fall upon a sensitive Thalofide cell and amplifying the electrical change produced. However, upon photographing the variations of the small lights about the same results were obtained as in the case of the small flashlight bulbs. The results were not satisfactory.

Affidavit in December 1922 Describing the Events of the Day

From the previous experiments with the incandescent flashlight bulbs both containing hydrogen and high vacuum, I do not believe that they could be made to work satisfactory as there was entirely too much continuous light and the impressed voice variations were too small in relation to the continuous light. On December 14, 1922 I then thought that the only solution would be to use a gas glow discharge. This I knew was what Dr. Lee deForest was using but he had been complaining that it did not work well in that it would continually fall down on him in that the light would go out when his voltage variations would fall below six thousand volts. The thing was unstable, sometimes it would ionize and sometimes it would not. This is as I understand the proposition from him. 

I then began thinking that there must be something we could do to the gas so that we could keep it in a ready state so that when the impulse came it would be easier to obtain ionization and discharge. From my past experience with the audion bulbs I thought that by putting a heated oxide coated filament into a bulb containing a vapor or gas and using it as one electrode and having the other electrode fairly close to it that the small impulses could more easily function in producing the glow. I thought first of trying mercury vapor in the bulb using some mercury as one electrode and the oxide coated filament as the other. This bulb was under process of construction when I remembered that I had some bulbs already made up containing some argon gas which occurred to me would be just the thing to use. These bulbs consisted of an oxide coated filament, argon gas at the appropriate pressure for best ionization and a grid and filament.

I had this bulb hooked up directly with the output of a four stage amplifying system; one terminal going to the heated filament and the other terminal to the grid. The microphone for taking up the voice variations was connected up to the input of the first bulb of the amplifying system through a transformer. The new light was heated and the results were most pronounced and pleasing. The voice variation after being transformed into the electrical variations produced a beautiful glow discharge in the argon bulb. The heated filament in its proper position was directly responsible for this result. Of course a gas should be used and was used which should be easily ionizable at the lowest possible voltage and which should emit a light rich in actinic rays so as best to produce photographic results.

We next took some pictures on moving picture film of these variations and upon developing a few minutes later found that the variations of the light were perfect and produced beautiful clear cut lines on the film which of course had been taken through a small slit. The film was moved about one foot a second past the slit. The light was on the opposite side of the slit from the film. The results were exactly what U had hoped for and far superior to anything that I had heretofore seen. I knew that this was what Dr. de Forest wanted so I proceeded to call Mr. Thompson, my patent attorney and explained my apparatus and the working of it to him. I then asked him if it would be alright for me to call Dr. de Forest on the phone and ask him to come up here as I knew this would solve the problem.

I took a piece of the film upon which I had photographed the word “hello” and installed this in the camera and passed it by the slit as near the same speed as we had taken it and by means of the Thalofide cell on the other side of the slit an incandescent light held so that it would shine through the film through the slit and on the the Thalofide cell head the word “hello” reproduced. Mr. Sponable also heard this reproduction. 

Several hours before Thompson had arrived and after we had first taken our pictures of this new light deForest called me by phone from New York and asked me if I could fill several small glass tubes for him with nitrogen gas at a pressure best suitable for ionization. I told him that I would do this for him. He then told me that was what he was using and that he was using between six and twelve thousand volts with his light and that he was having great trouble with it as it was uncertain in its action and would fall down at times and times would not start. I did not tell him during this telephone conversation what I had done to correct this difficulty but thought that I had better wait until I had talked with Mr. Thompson. That evening after Thompson had told me that I could have deForest see it, I called de Forest on the telephone and told him that I had a new development and asked him to come to Auburn on the night train which he did.

Dr. DeForest arrived early in the morning of December 15, 1922 and we proceeded to the laboratory where I showed him my new light in action. He was very much pleased. I also showed him some pieces of the film I had taken. He said that they were very remarkable. He never saw such pictures of voice variations so good and he was pleased with the whole thing. He said on looking at the light that it was the gas I was using that was responsible for the whole thing. I told him it was not the gas alone but that it was due to the heated oxide coated filament placed in the bulb which energized the gas and allowed the small currents of relatively small voltage from the amplifying system to perform their function much more easily and produce the glow discharge. The glow discharge started instantly as everything was prepared for it by the heated filament. Of course the distance between the grid and filament was quite short which was quite necessary as the ionizing work should be kept down to as small a factor as possible. 

He remarked that it was perfectly fine and desired to take one of these bulbs back with him immediately so I loaned him one to work with. The shape of the bulb which was round was not exactly suited to fit into the camera so a design was talked of which would fit in so that he would not have to change his camera and the following was determined upon. The essentials were not changed that is a heated oxide coated filament and a conductor in very close proximity with argon gas at the correct pressure. I then learned that several years ago he had tried a tungsten filament in a long bulb containing hydrogen gas. This sketch drawn by him is included and he said that he had not obtained any results with it, that he had seen no advantage and therefore had dropped the idea. The reason that it had not worked for him was probably because of the distance between the heated filament and the other electrode, plus the fact that he was using a gas which would not ionize as easily as argon.It would be another serious disadvantage in using a tungsten filament namely the light from it would be actinic enough to badly effect the photograph film whereas in the case of the oxide coated filament there are no actinic rays and the glow discharge acts as the sole photographic agency. Appended to this is shown some photographs of the hook-up used with my new lamp with short explanations. Dr. DeForest returned to New York that night.

On December 16, 1922 I did some further work with the system and found that by adjusting the resistance of the primary transformer coil which was in series with the microphone that I got very much greater fluctuations than the day before. The resistance had been too high in comparison with the resistance of the microphone and therefore the microphone had not been functioning in its fullest capacity. With this error corrected whispers at twenty-five or thirty feet from the apparatus were reproduced beautifully. All sorts of sounds and combinations of words were tried. I then had a six foot length of motion picture film installed and took by means of this new light the entire alphabet spoken by myself plus a few words at the end. Upon developing this it all came out beautifully. Dr. DeForest had the idea of using a glow discharge. It was hard to do this however with the present art and it gave him a great deal of trouble. What I added was a factor which made the action easy, simple and practical so that the thing would work at all times plus the fact that I used a gas which was more easily ionizable than he had been using but the essential thing in the bulb was the energizing coated filament with not too great a distance between it and the other electrode. Pieces of the first film taken with this light before Dr. DeForest arrived are attached to this affidavit.

Earl I. Sponable was with me during these experiments and assisted me with them. He also heard Dr. DeForest mention the fact that he had tried the tungsten filament, saw him draw the diagram of the tube he used, which diagram is affixed hereto and also heard him say that he had obtained no results by the additions of the filament, saw no advantage in it and had dropped it.

Today, perfectly synchronized, clear sound is so commonplace in our media that it is easier to tell when something is wrong than to celebrate it being right. Imagine your favorite movie line, or even your favorite movie at all. Imagine the news, Youtube videos, TikTok, all of these essentially sound based mediums combined with visual platforms. How would you process these mediums differently without being able to hear them? That is the question that Ted Case, Earl Sponable, and all the workers in the Case Research Laboratory first made redundant on December 14, 1922.