John Logie Baird (1888-1946)

TELEVISION
                   AND
SHORT- WAVE WORLD

MARCH, 1938

[NLS note: a graphic appears here – see image of page]

the Crystal Palace, and it was ap-
parent what excellent reproduction
had been obtained.

There are some very interesting
features about this apparatus and a
very large number of practical diffi-
culties had to be solved before it
could be put into successful opera-
tion. One trouble was in the con-
struction of a mirror drum that at
the high speed of revolution would
not distort the mirrors or burst. De-
pending upon the method of securing
the mirrors to the drum, they would
either bend outwards and become
convex or inwards and become con-
cave until a suitable method of con-
struction had been developed. The
fire regulations of the L.C.C. had
also to be overcome and this necessi-
tated the entire receiver and projector
being enclosed in metal cases with
only a small peephole through which

the arc crater could be observed. This
latter, by the way, takes a current of
150 amps. and the heat generated
makes water cooling essential.

The general layout of both trans-
mitter and receiver will be clear from
the schematic drawings and it will be
seen that the drum and disc are
directly coupled together by means
of reducing gearing, one motor being
used to drive both. The Kerr cell
used for light modulation is of the
ordinary type with an aperture about

3/16 in. square. Other types of cell
using both rays were tried, but it was
found that gains obtained in one
direction were more than lost in
others and that the ordinary type
gave the best results. Actually
the transmitter is mounted on a bogie
of much the same type as is used for
the Emitron camera and it is there-
fore reasonably flexible in use. The
entire apparatus is a beautiful piece
of work and reflects great credit on
the production engineers of the Baird
Company.

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