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Dead medium: Early/Mechanical Television Systems
From: kadrey@well.com Richard Kadrey
Source(s): These are excerpts from the catalog from the exhibition at the Royal Ontario Museum, "Watching TV". The exhibition runs through September 15, 1996.

The catalogue is available from Royal Ontario Museum shops, CityStore 299 Queen Street, West, Ontario, Canada or from MZTV Museum. Cost - $11.50 Cdn., $10.00 US, plus shipping. Send email orders to mztv@bravo.ca

Credits: An excerpt from "Watching TV: Opening the Doors of Reception" by Liss Jeffrey, Acting Director, MZTV Museum. Technical research by Gary Borton, Consulting Curator, and Iain Baird, Researcher, MZTV Museum.

"Mechanical TV: Pioneering Experiments"Mechanical TV: The Pioneers

Nipkow

One of the earliest proposals for a mechanical television

system was put forward by German researcher Paul Nipkow in

1883. When he developed patent No. 30,105, he was an

unknown twenty-three-year-old student living in Berlin. It

proved to be the basis for most early television schemes

in the world, although he never built the apparatus.

In Nipkow's patent, which he called an 'electric

telescope,' a disc was punched with holes in a spiral near

the outer edge. When the disc revolved, each hole

vertically scanned a line of the image, allowing

variations in light to reach a selenium cell. As one hole

swept over a segment of the picture, the next in sequence

tackled the portion next to it, until the complete subject

had been scanned.

The selenium cell transferred the light variations to

an electronic signal. Pictures were reconstituted at the

receiver by a similar disc which was synchronized with the

transmitter.

Jenkins

One of the better known experimenters with mechanical

television was Charles Francis Jenkins, a prolific

American inventor. In May 1920, at the Toronto meeting of

the Society of Motion Picture Engineers, Jenkins

introduced his "prismatic rings" as a device to replace

the shutter on a film projector. This invention laid the

foundation for his first radiovision broadcast.

He claimed to have transmitted the earliest moving

silhouette images on June 14, 1923, but his first public

demonstration of these did not take place until June of

1925.

Jenkins Laboratories constructed a radiovision

transmitter, W3XK, in Washington D.C. The short-wave

station began transmitting radiomovies across the Eastern

U.S. on a regular basis by July 2, 1928. Jenkins wrote in

1929: "This gave the amateur action-pictures to 'fish'

for; and during August following a hundred or more had

finished their receivers and were dependably getting our

broadcast pictures, and reporting thereon, to our great

help."

It was in this way that Jenkins actively promoted

enthusiasm and experimentation in the short-wave radio

community, and the U.S. experienced its first television

boom, with an estimated 20,000 lookers-in.

Baird

John Logie Baird, a Scottish engineer and entrepreneur,

achieved his first transmissions of simple face shapes in

1924 using mechanical television. On March 25, 1925,

Baird held his first public demonstration of "television"

at the London department store Selfridges on Oxford Street

in London. In this demonstration, he had not yet obtained

adequate half-tones in the moving pictures, and only

silhouettes were visible.

In the first week of October, 1925, Baird obtained

the first actual television picture in his laboratory. At

this time, his test subject was a ventriloquist's dummy,

"Stooky Bill," which was placed in front of the camera

apparatus.

Baird later recollected, "The image of the dummy's

head formed itself on the screen with what appeared to me

an almost unbelievable clarity. I had got it! I could

scarcely believe my eyes and felt myself shaking with

excitement."

After much discussion with his business associates,

and further improvements, Baird decided to publicly

demonstrate television on Tuesday 26 January, 1926, again

at Selfridge's department store. This was the first

opportunity for the general public to see television.

The Baird company continued to publicize this

historic demonstration, and J. L. Baird's other scientific

breakthroughs as they feverishly worked to obtain

financial backing and construct a line of home receivers.

With Baird's transmitting equipment, the British

Broadcasting Corporation began regular experimental

television broadcasts on September 30, 1929. By the

following year, most of Britain's major radio dealers were

selling Baird kits and ready-made receivers through retail

and by mail order.

Richard Kadrey (kadrey@well.com)