Part 3
And as these discolored dots-and-dashes appear, as before, in an order controlled by the distant station, a picture is again built up on the paper, a copy of the picture at the sending station.
One of the best solutions for the purpose is made up of Iodide of Potassium one-half pound; Bromide of Potassium two pounds; Dextrine or Starch one ounce; and Distilled Water one gallon. (Use an iron contact needle). There are other solutions made of Ferricyanide, but are not so satisfactory.
Still another scheme, the simplest of mechanisms, consists of a metal disc upon which electrolytic paper is clipped. This plate is then put on the rotating table of a talking machine. A rubbing electrical contact is made with the disc, and the other wire attached to the tone arm to complete the circuit through the steel needle of the sound box.
As no groove is available to carry the arm toward the centre of the disc, a spurred-wheel is attached thereto, so as to engage the paper on the disc. The wheel can be adjusted diagonally of the tone arm to give any separation required in the convolutions of the spiral line.
One of the schemes employed, and with considerable success for its time, consisted of an engraving tool, moved up and down radially of a coated cylinder, cutting a groove of varying width in the soft coating of the cylinder.
When this coating was stripped off the cylinder, laid out flat and hardened, it was mounted on a printing block, inked, and impressions taken therefrom on a suitable printing press.
PHOTOGRAPHIC RECEIVERS:
But doubtless photographic paper, wrapped around the cylinder, has been used oftener than any other medium. With photo paper or film a point of light is usually employed to expose the film.
OSCILLOGRAPH RECEIVERS:
The point sources of light used and methods of modulation have been almost as varied as the temperaments of the several workers. One of the first was the employment of a steady light source which, reflected in the tiny mirror of an oscillograph, is caused to vibrate at a high frequency across a minute aperture which in turn is imaged on the film on the cylinder. As the amplitude of vibration of the mirror determines the amount of light passing through the aperture and falling on the film, it will readily be understood that the strength of the incoming electric signals, representing light values of the picture at the distant station, reproduce duplicate values on the exposed film. When this film is developed a copy of the picture on the cylinder of the sending machine is obtained.
LIGHT WEDGE MODULATION:
Another scheme for modulating the light falling on the film on the cylinder, consists in placing a light wedge against the face of a lens which images the vibrating mirror (or light source) on the film.
As the light is constantly imaged on the film by the lens its slight displacement toward the dark end of the light wedge by the vibration of the mirror decreases the strength of the light falling on the film, while displacement toward the thin edge of the light wedge gives greater exposure on the film.
It is obvious, therefore, that the vibration of the mirror determines the exposure at successive positions on the film; and as these displacements follow the varying strength of the incoming electric current, and the latter in turn is determined by the light values of the picture at the sending station, it naturally follows that when the film is developed a duplicate of the distant picture results.
SILVER WIRE GALVANOMETER:
Another method of varying the light falling on the photo film on the cylinder consists in mounting two very minute overlapping shutters one on each of the two wires of an electric circuit suspended in a strong magnetic field. On these overlapping shutters a light source is focused, so that greater or lesser displacement of the shutters, by reason of varying strengths of current in the adjacent runs of the wire, allows more or less light to pass there between.
Another lens images these tiny shutters onto the film covered cylinder, so that when the shutters are opened by the incoming currents in the two wires, the light is concentrated on the film.
As the exposure depends on (_a_) the shutter openings, and the shutter opening on (_b_) the incoming current strength, and the incoming current strength on (_c_) the light values at the sending station, development of the film again gives a duplicate of the picture at the sending station.
PNEUMATIC VALVE:
An interesting scheme of picture reception is known as the pneumatic light valve, the vibration of which causes a shadow band to oscillate across a lens opening into the camera.
In a circular center opening in a magnetized iron diaphragm is suspended an iron disc somewhat smaller than the opening. This small disc is magnetically held by its edge to the inside edge of the opening in the diaphragm, with its plane in the plane of the magnetic field of the diaphragm.
Upon the disc is mounted a tiny mirror, and as the suspension of the disc is in the magnetic field held there by the strength of the field itself, it is extremely easily disturbed, so that a small beam of light reflected from the mirror can be vibrated with a very little current through great amplitude.
As the beam of light has a transverse shadow band therein of a width to normally close the lens opening into the camera, the varying amplification of the vibration of the mirror, and therefore, of the shadow, admits a proportional amount of light.
SPARK GAP:
One of the very simplest light sources for exposing the film on the receiving cylinder consists of a minute spark-gap located in contact with the moving film.
The strength of the incoming current charges a small condenser until the gap breaks down and the passing spark exposes the film (or perhaps perforates it). If the current is strong the sparks pass the gap at a high frequency, while if the current is weak the frequency is less. The range may be from 500 to 5,000 per second perhaps, depending on the current strength, and, of course, the film exposure correspondingly varies, and the different degrees of density of the picture results.
This scheme requires about as small current as is likely to be practical, perhaps, especially when the spark is in a suitable degree of vacuum, and, of course, the incoming radio signals require correspondingly small amplification.
FILAMENT LAMP:
The direct source of light which in the author’s laboratory has produced the most perfect photographic effects, i. e., photographs absolutely without lines, consists of a lamp about an inch in diameter and two inches long, fitted with a standard screw base. The tube contains a .6 mil filament with a small single turn coil in a hydrogen atmosphere.
The coil is offset until it almost touches the glass wall. Such location of the coiled filament permits the effective placing of a minute aperture in very close relation to the filament; whereas an aperture on the outside of a bulb with the light source in the centre of the bulb acts like a pin-hole camera, and sharpness of image is practically impossible (unless a lens is used).
The lamp described above will respond to fluctuations in current well above a thousand times per second, but requires voltages about four times normal. It was made for the author by courtesy of the General Electric Company, under the direction of Mr. L. C. Porter, of Harrison, N. J.
CORONA LAMP:
But the lamp that really elicits the author’s unqualified admiration is the corona glow lamp made for the author by Professor D. McFarlan Moore. It consists of a small glass bulb containing a neat-fitting metallic cylinder, one terminal of an attached circuit. Inside and concentric with the cylinder is a second cylindrical capsule made of a solid rod drilled to a predetermined depth.
The electron stream from the outside cylinder to the capsule naturally takes the long path, and as the longest path is down into the capsule, the result is that the small central opening of the capsule glows with great intensity while the other parts of the lamp remain dark. This lamp, Professor Moore advises, has a light and dark frequency of a million per second.
[Illustration: WESTERN UNION TELEGRAM NEWCOMB CARLTON, PRESIDENT GEORGE W. E. ATKINS, FIRST VICE-PRESIDENT 153W 1W 1 EXTRA OF TELEPHONED MESSAGE P ROCHESTER NY 114P OCT 12 1922 C FRANCIS JENKINS 1519 CONN AVENUE NW WASHINGTON DC SOCIETY MOTION PICTURE ENGINEERS REGRETS YOUR ABSENCE FROM THE CONVENTION BEST WISHES FOR YOUR SUCCESS IN RADIO TRANSMISSION OF PICTURES A R DENNINGTON SECY 225P]
WESTERN UNION
TELEGRAM
NEWCOMB CARLTON, PRESIDENT GEORGE W. E. ATKINS, FIRST VICE-PRESIDENT
153W 1W 1 EXTRA OF TELEPHONED MESSAGE
P ROCHESTER NY 114P OCT 12 1922
C FRANCIS JENKINS
1519 CONN AVENUE NW WASHINGTON DC
SOCIETY MOTION PICTURE ENGINEERS REGRETS YOUR ABSENCE FROM THE CONVENTION BEST WISHES FOR YOUR SUCCESS IN RADIO TRANSMISSION OF PICTURES
A R DENNINGTON SECY
225P
[Illustration: GENERAL ELECTRIC COMPANY In Reply Refer to WEST LYNN, MASS. November 28, 1922. Mr. C. Francis Jenkins, 1519 Connecticut Ave., Washington, D.C. Dear Mr. Jenkins: I am in receipt of yours of November 25th, enclosing the radio picture, for which I thank you. It certainly shows a successful result. When I first read of your prismatic ring arrangement in the “Scientific American”, I recognized that it was the solution of a problem which I had often thought of as possible, and I can well understand that it may have applications which we do not even now think of. It is perfectly possible, as you say, to employ the method of radio transmission of pictures on a very considerable scale, which would hardly be possible in transmitting them by the ordinary telegraph. With best regards, and gratification to know that you are progressing, I am, Very truly yours, Elihu Thomson]
GENERAL ELECTRIC COMPANY
In Reply Refer to
WEST LYNN, MASS.
November 28, 1922.
Mr. C. Francis Jenkins, 1519 Connecticut Ave., Washington, D.C.
Dear Mr. Jenkins:
I am in receipt of yours of November 25th, enclosing the radio picture, for which I thank you. It certainly shows a successful result.
When I first read of your prismatic ring arrangement in the “Scientific American”, I recognized that it was the solution of a problem which I had often thought of as possible, and I can well understand that it may have applications which we do not even now think of. It is perfectly possible, as you say, to employ the method of radio transmission of pictures on a very considerable scale, which would hardly be possible in transmitting them by the ordinary telegraph.
With best regards, and gratification to know that you are progressing, I am,
Very truly yours,
Elihu Thomson
[Illustration: THE WHITE HOUSE WASHINGTON December 5, 1922. Dear Mr. Jenkins: Please accept my thanks for the radio photograph which you were good enough to send to me. The production of a picture in this fashion is certainly one of the marvels of our time and I am under obligation to you for sending me this handsomely mounted copy which will be preserved as a very much prized souvenir. Gratefully yours, Warren G Harding Mr. C. Francis Jenkins 1519 Connecticut Avenue, Washington, D.C.]
THE WHITE HOUSE
WASHINGTON
December 5, 1922.
Dear Mr. Jenkins:
Please accept my thanks for the radio photograph which you were good enough to send to me. The production of a picture in this fashion is certainly one of the marvels of our time and I am under obligation to you for sending me this handsomely mounted copy which will be preserved as a very much prized souvenir.
Gratefully yours,
Warren G Harding
Mr. C. Francis Jenkins 1519 Connecticut Avenue, Washington, D.C.
[Illustration: Westinghouse Electric & Manufacturing Company East Pittsburgh, Pa. Mr. C. Francis Jenkins, 1519 Connecticut Ave., Washington, D.C. March 7, 1923. My dear Jenkins: I have been reading with much interest the newspapers giving an account of your success in sending photographs by Radio from Washington to Philadelphia. After my visit to your laboratory a few weeks ago when you told me of this proposed transmission, I have been looking forward to it feeling assured it would be fully as successful as the papers have related, and I want to add my congratulations to the many you must have already received, and which you so well deserve. May your success continue. With kindest regards, I am, Yours very sincerely, John]
Westinghouse Electric & Manufacturing Company East Pittsburgh, Pa.
Mr. C. Francis Jenkins, 1519 Connecticut Ave., Washington, D.C.
March 7, 1923.
My dear Jenkins:
I have been reading with much interest the newspapers giving an account of your success in sending photographs by Radio from Washington to Philadelphia. After my visit to your laboratory a few weeks ago when you told me of this proposed transmission, I have been looking forward to it feeling assured it would be fully as successful as the papers have related, and I want to add my congratulations to the many you must have already received, and which you so well deserve. May your success continue.
With kindest regards, I am,
Yours very sincerely,
John
[Illustration: THE FRANKLIN INSTITUTE OF THE STATE OF PENNSYLVANIA PHILADELPHIA March 8, 1923. Mr. Francis Jenkins, 5502 Sixteenth Street,N.W., Washington, D.C. My dear Mr. Jenkins: I want to say to you how delighted I was to receive your letter of March 6th, accompanied by the beautiful examples of your success in transmitting photographs by radio. I enjoyed very decidedly the opportunity that you gave me of seeing the process of receiving these pictures and have found since that a number of those whose attention I called to your work, took advantage of the opportunity and were greatly pleased with the results. I can only say that I appreciate to a certain extent, at least, the tremendous energy and persistence that you have put into the development of this new art and most heartily congratulate you on the success that you have obtained. I am promising myself that if I come to Washington at any time in the near future to make a visit to your laboratory and see you in your own private lair. Hoping that such an opportunity will not be too long delayed. I am, Sincerely yours, Geo. A. Hoadley. S. and A. Assistant.]
THE FRANKLIN INSTITUTE OF THE STATE OF PENNSYLVANIA PHILADELPHIA
March 8, 1923.
Mr. Francis Jenkins, 5502 Sixteenth Street,N.W., Washington, D.C.
My dear Mr. Jenkins:
I want to say to you how delighted I was to receive your letter of March 6th, accompanied by the beautiful examples of your success in transmitting photographs by radio. I enjoyed very decidedly the opportunity that you gave me of seeing the process of receiving these pictures and have found since that a number of those whose attention I called to your work, took advantage of the opportunity and were greatly pleased with the results.
I can only say that I appreciate to a certain extent, at least, the tremendous energy and persistence that you have put into the development of this new art and most heartily congratulate you on the success that you have obtained.
I am promising myself that if I come to Washington at any time in the near future to make a visit to your laboratory and see you in your own private lair. Hoping that such an opportunity will not be too long delayed. I am,
Sincerely yours,
Geo. A. Hoadley.
S. and A. Assistant.
[Illustration: CHARLES FRANCIS JENKINS 232 SOUTH 7TH STREET PHILADELPHIA, PENNA. March 12th, 1923. Charles Francis Jenkins, Washington, D.C. Dear Friend: The receipt of the Journal of the English Historical Society a few days ago, in which is given a list of Friends who have achieved distinction through inventions and in which your name is given, shows that we have another point of contact in addition to our exactly similar names, and that is, we are both Members of the Society of Friends. If you ever get to Philadelphia, I hope you will stop in and see me and arrange to have lunch with me, if possible. I have been much interested in the considerable amount of publicity given your work lately and I enclose a page from the Evening Bulletin, although I think it more than likely you have seen it. With best wishes, Very truly, Charles Francis Jenkins]
CHARLES FRANCIS JENKINS 232 SOUTH 7^{TH} STREET PHILADELPHIA, PENNA.
March 12th, 1923.
Charles Francis Jenkins, Washington, D.C.
Dear Friend:
The receipt of the Journal of the English Historical Society a few days ago, in which is given a list of Friends who have achieved distinction through inventions and in which your name is given, shows that we have another point of contact in addition to our exactly similar names, and that is, we are both Members of the Society of Friends.
If you ever get to Philadelphia, I hope you will stop in and see me and arrange to have lunch with me, if possible.
I have been much interested in the considerable amount of publicity given your work lately and I enclose a page from the Evening Bulletin, although I think it more than likely you have seen it.
With best wishes,
Very truly,
Charles Francis Jenkins
[Illustration: NAVAL RESEARCH LABORATORY “BELLEVUE,” ANACOSTIA, D. C. 21 August 1923. Mr. C. F. Jenkins, 1519 Connecticut Ave., Washington, D.C. My dear Jenkins: Thanks very much for the samples of your recent work. They look very good. I was particularly interested in what you said concerning the Chinese and Japanese methods of transmitting telegraphy. I had heard something of this before but never realized how complicated it would make the process for them. As soon as I can get this laboratory well started I will certainly find time to look in on you and I hope arrangements may be made for continuing some cooperative work with you. We have designated a section of our organization to work on methods of secret communication but just now we are unable to put anyone on that work. I hope you will keep me in touch with your developments and let me know in particular what progress you are making towards high speed work. One of the best arguments that I can make for the Navy taking up such work will be the matter of saving time in handling coded messages. With best regards, I am, Very truly yours, A. Hoyt Taylor Physicist, USN]
NAVAL RESEARCH LABORATORY
“BELLEVUE,” ANACOSTIA, D. C.
21 August 1923.
Mr. C. F. Jenkins, 1519 Connecticut Ave., Washington, D.C.
My dear Jenkins:
Thanks very much for the samples of your recent work. They look very good. I was particularly interested in what you said concerning the Chinese and Japanese methods of transmitting telegraphy. I had heard something of this before but never realized how complicated it would make the process for them.
As soon as I can get this laboratory well started I will certainly find time to look in on you and I hope arrangements may be made for continuing some cooperative work with you. We have designated a section of our organization to work on methods of secret communication but just now we are unable to put anyone on that work.
I hope you will keep me in touch with your developments and let me know in particular what progress you are making towards high speed work. One of the best arguments that I can make for the Navy taking up such work will be the matter of saving time in handling coded messages.
With best regards, I am,
Very truly yours,
A. Hoyt Taylor
Physicist, USN
[Illustration: POPULAR RADIO 9 EAST 40TH STREET, NEW YORK KENDALL BANNING, _Editor_ _Vanderbilt 9985_ September 11, 1923. C. Francis Jenkins,Esq., 1519 Connecticut Avenue, Washington, D.C. My dear Mr. Jenkins: I certainly appreciate your interesting letter of September 10th, as well as the three photographic enclosures. I am tremendously impressed, not only with what you have accomplished in the transmission of pictures by radio, but also with the limitless possibilities that you are opening up. It is entirely conceivable that the work you are doing right now may have an effect upon civilization that will be almost revolutionary. You must have had a corking good time on your airplane trip from Omaha to Chicago. Yes, we have been, undoubtedly backward in the development of our airplane commercial traffic. Some day we will make up for lost time. Cordially, Kendall Banning]
POPULAR RADIO 9 EAST 40^{TH} STREET, NEW YORK
KENDALL BANNING, _Editor_ _Vanderbilt 9985_
September 11, 1923.
C. Francis Jenkins,Esq., 1519 Connecticut Avenue, Washington, D.C.
My dear Mr. Jenkins:
I certainly appreciate your interesting letter of September 10th, as well as the three photographic enclosures. I am tremendously impressed, not only with what you have accomplished in the transmission of pictures by radio, but also with the limitless possibilities that you are opening up. It is entirely conceivable that the work you are doing right now may have an effect upon civilization that will be almost revolutionary.
You must have had a corking good time on your airplane trip from Omaha to Chicago. Yes, we have been, undoubtedly backward in the development of our airplane commercial traffic. Some day we will make up for lost time.
Cordially,
Kendall Banning
[Illustration: IMPERIAL JAPANESE NAVY INSPECTORS’ OFFICE ONE MADISON AVENUE New York City October 6, 1923. Dr. C. Francis Jenkins, Radio Pictures Corporation, Washington, D.C. Dear Dr. Jenkins: Thank you for your kind note of October 4th enclosing some splendid reproductions of the message I wrote when I called upon you at your Laboratory. Upon my return to Japan, I shall inform our Home authorities about the merits of your high speed camera and radio apparatus and will also present the fine samples you sent me. By the way, kindly accept this expression of gratitude for the courtesies you extended to me and my associates during our recent visit to Washington. Very truly yours, T. Kuroda ENGINEER_CAPTAIN, I. J. N.]
IMPERIAL JAPANESE NAVY
INSPECTORS’ OFFICE
ONE MADISON AVENUE
NEW YORK CITY
October 6, 1923.
Dr. C. Francis Jenkins, Radio Pictures Corporation, Washington, D.C.
Dear Dr. Jenkins:
Thank you for your kind note of October 4th enclosing some splendid reproductions of the message I wrote when I called upon you at your Laboratory.
Upon my return to Japan, I shall inform our Home authorities about the merits of your high speed camera and radio apparatus and will also present the fine samples you sent me.
By the way, kindly accept this expression of gratitude for the courtesies you extended to me and my associates during our recent visit to Washington.
Very truly yours,
T. Kuroda
ENGINEER_CAPTAIN, I. J. N.
[Illustration: Commonwealth of Pennsylvania Governor’s Office HARRISBURG October 23, 1923. Mr. C. Francis Jenkins, 5502 Sixteenth Street, Washington, D.C. Dear Mr. Jenkins: My heartiest thanks for your letter of October 17th and for the copy of my first photograph by radio. I appreciate it more than I can easily say, and think it is a perfectly marvelous piece of work under the circumstances. Also it is more than pleasant to have it from you, in view of our long association, and so beautifully mounted. With renewed appreciation, and heartiest thanks for all the trouble you took in getting it up. Sincerely yours, Gifford Pinchot]
Commonwealth of Pennsylvania
Governor’s Office
HARRISBURG
October 23, 1923.
Mr. C. Francis Jenkins, 5502 Sixteenth Street, Washington, D.C.
Dear Mr. Jenkins: