Saturday, 1 April 2017

Thomas Edison's "Telephonoscope" of 1878 - Transmits Light as Well as Sound


An 1879 Representation of Thomas Edison's "Telephonoscope" in use

Thomas Edison is remembered primarily as the inventor of the incandescent electric light bulb. But Edison was also an accomplished inventor and businessman with a prolific 1,093 US patents to his name. A few of his other more widely known inventions are the cylindrical phonograph for permanently recording and playing sound, the carbon microphone used in all telephones until the 1980's, and the "Kinetoscope" for viewing motion pictures.  

But do you believe that "Skyping" is an invention of the modern age? Well think again. One of Edison's more interesting and technologically advanced but lesser known inventions was his 1878 "Telephonoscope", an apparatus which enabled the transmission of not only sound - but also of light. The above representation of the device in operation by George Du Maurier gives us is an accurate representation of this apparatus in actual use, truly an optical "electric camera obscura" but also with sound.

"The Electroscope", published by the
"New York Sun", 29th March 1877

The "New York Sun" heralded this new invention on the 29th March 1877 when it announced that "an eminent scientist of this city" [being of course Edison at Menlo Park] was on the point of "exhibiting an instrument invented by him by means of which objects or persons standing or moving in any part of the world may be instantaneously seen anywhere and by anybody. The utility of the "electroscope" [as it was initially termed] is undeniable, and if the invention proves succesful it will supersede in a very short time the ordinary methods of telegraphic and telephonic communication." 


The Theory of "The Electroscope", published
by the "New York Sun", 29th March 1877

It is this machine that Edison had by 1878 perfected into the new "Telephonoscope". The theory behind the "telephonoscope" is simple, well at least to us in this technogically advanced age. A "camera obscura", of which there is a well known example in Edinburgh, optically captures an outside image and projects it on to a screen in a darkened room. But by means of converting that optical image into rapid electrical impulses by projecting that image onto a complex system of many thousands of light sensing wires the impulses may then be transmitted over copper wires using the same principle as a telephone voice transmission but obviously using a more technologically advanced receiver and transmitter. 

A similar battery powered apparatus at the receiving end is then used to convert the electrical impulses back to an optical and sound image using a receiver containing a newly discovered gas, "a sort of magnetic electric ether".The resultant optical image would then be projected onto a screen by means of a mirror and Edison's incandescent light. The sound would be transmitted by the normal method for telephonic communication. This then enabled one-way picture transmission (albeit of low picture quality) and two-way sound communication.   

Du Maurier's caption reads; "Every evening, before going to bed, Pater and Materfamilias set up an electric camera-obscura above their bedroom mantlepiece, and gladden their eyes with the sight of their Children at the Antipodes [in this case Ceylon], and converse gaily with them through the wire".   


The "moving image" transmitted by the "Telephonoscope"
from the other side of the world - in "cinemascope" no less.

You will observe the "speaking and listening tubes" in use by the grandparents in London in the image at the top of this page while a daughter in Ceylon holds a similar device at the other end. Their conversation is recorded as being:

Paterfamilias (in Wilton Place [London]): “Beatrice, come closer, I want to whisper."
Beatrice (from Ceylon): “Yes, Papa Dear.”
Paterfamilias: "Who is that charming young lady playing on Charlie’s side?"
Beatrix: “She’s just come over from England, Papa. I’ll introduce you as soon as the Game’s over?” 


But the heavy expense of the equipment coupled with the complexities of having not only a receiver but also a transmitter at the source, the "cutting-edge" technology yet to be fully perfected, the difficulties and prohibitive cost of communicating via an unreliable and expensive copper cable network designed for telephone and telegraph use, effectively transmitting that electrical communication - in this case half way around the world - and the need for amplification of the transmission [achieved by the use of "loading coils"] over longer distances not to mention the problem of voltage fluctuations, echoes and static electrical disturbances on the line disrupting the signal would all contribute to the Telephonoscope not becoming the hoped for commercial success that Edison had envisaged.  

Still skeptical? In 1891 it was reported by none other than "The New Zealand Herald" [19th June 1891, p6] that Edison, obviously not one to accept defeat, was then perfecting and intended exhibiting his now so-called "Photo-Phonographic Machine" at the great Chicago World's Fair of 1893. But instead of transmitting the signal by air waves in what we would today called "Television", the signal would be sent to multiple viewers and any number of receivers but still via copper wires. It is interesting that he was aiming this new device at a different market, undoubtedly with the aim of now making it a commercially viable proposition by way of entertainment. Evidently Edison foresaw the practical advantages of what we know today as Cable Television

[Source : "New Zealand Herald", 19 Jun 1891]

"I hope by this invention to throw upon canvas a perfect picture of anybody and reproduce his words. Thus, should [Adelina] Patti be singing somewhere this invention will put her full-length picture upon canvas so perfectly as to enable one to distinguish every feature and expression of her face, see all her actions, and listen to the entrancing  melody of her peerless voice.. The invention will do for the eye what the phonograph has done for the voice, and reproduce the voice as well; in fact more clearly."

"I have already perfected the invention so far as to be able to picture a prize fight, the two men in the ring, and the intensely interested faces of those surrounding it. You can hear the sound of the blows, the cheers of encouragement and yells of disappointment."

"And when this invention shall have been perfected", added Mr Edison... "A man will be able to sit in his library, and having electrical connection with a theatre, have reproduced on his wall or a piece of canvas the actors and hear anything they say. The only thing the invention wants is the finesse to reproduce the most delicate features and expressions."  

"Concert and Opera at Home" -
A prediction for a form of television "One Hundred years hence" 

Edison was truly "America’s greatest inventor" but also a brilliant man well ahead of his time.

Blog Published 1st April 2017


Bibliography :

- Various Internet Sources
- Wikipedia
- "Papers Past" [National Library of New Zealand / Te Puna Mātauranga o Aotearoa]

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