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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: Baird Television"
The ROM's Institute of Contemporary Culture in
association with the MZTV Museum invites you to join us
for an historic demonstration of BAIRD TELEVISION, live at
the Royal Ontario Museum, Sunday April 14th, 1996, 1:00pm.
John Logie Baird is the Scottish inventor who
obtained the world's first real television picture in his
laboratory in October, 1925, and demonstrated it to the
British public on January 26, 1926. The image
obtained was a small 30-line vertically-scanned red and
black image, but it was television. Mechanical television
based on Baird's systems dominated international
television for the next few years into the early 30's.
The first live public demonstration of a Baird
Television system in North America since 1932 will take
place in Toronto on Sunday, April 14th. John Logie Baird's
son, Professor Malcolm Baird, will give a short speech to
commemorate the 70th anniversary of the first public
demonstration of television; grandson Iain Baird, who
presently works at MZTV, will be in attendance to operate
Mechanical systems of this period are not
compatible with today's TV signals. When the MZTV Museum
decided to restore this televisor to full operation, the
first obstacle was to feed a signal to it that it could
receive. We requested the assistance of Peter Yanczer, a
modern-day mechanical television enthusiast, author, and
technician. He built a mechanical camera that would work
on a 30-line system, and connected this camera to the
television with cables. The televisor itself needed only
minor repairs and lubrication, and has remained workable.
By 1930, a British or West European television
enthusiast could buy this televisor for home reception for
about 18 pounds. The Baird company was licensed to provide
intermittent broadcasts from the BBC transmitters, and at
least 3,000 enthusiasts "looked in" to see as well as hear
some of Britain's most popular singers and comedians.
Mechanical TV: How it works
The scanning and reproducing discs are similar. Both are
mounted on driving motors, and each is punched with a
spiral of small holes along the outer edge. The number of
holes matches the number of lines of picture definition.
At the transmitter in this mechanical system, the
studio is in total darkness. A light emanates from a lamp
behind the disc and, projected through the holes set in
the spiral on the outer edge, scans the features of the
subject's face. The photocell converts these variations
in the reflected light into the electric impulses, which,
once amplified, can be transmitted by radio waves.
At the receiver, the signal is converted into a
sequence of bright flashes by the neon tube. The
reproducing disc rotates rapidly in front of this tube,
and converts each flash of the lamp into a small element
of the image. The rapid speed of the disc makes
"persistence of vision" possible for the looker-in.
"Persistence of vision" means that the brain retains
an image for one tenth of a second after it is perceived
by the eye. The rapid repetition of moving images (in film
or television) tricks the brain into perceiving continuous
Richard Kadrey (firstname.lastname@example.org)