Movies for TV - Early Television Foundation

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FUNDAMENTALS
the lower. The lower is again broken by the introduction of a small,
mobile service band between channels four and five. Shown below
are the channel numbers and the corresponding frequencies.
Low Band High Band
Channel Megacycles Channel Megacycles
2 54 to 60 7 174 to 180
3 60 to 66 8 180 to 186
4 66 to 72* 9 186 to 192
5 76 to 82 10 192 to 198
6 82 to 88 11 198 to 204
12 204 to 210
13 210 to 216
* The band 72 to 76 megacycles is used for mobile phone, thus
making it possible to use channels four and five in the same city.
The Film Chain Camera The camera used to transmit films
over television employs the older iconoscope tube. This was the fore-
runner of the image orthicon and is reputed to give better quality
than the latter although it requires more light. The Pye Radio Com-
pany of Cambridge, England, has recently introduced an image
iconoscope and has named it the Photicon. The "image" prefix
usually means that a multiplier section has been incorporated in
the iconoscope to amplify the very weak signals from the mosaic
before passing them on to the rest of the equipment. This in turn
ensures the minimum of noise being amplified in the rest of the
equipment. The Photicon gives beautiful definition and resolution
but requires a little more light than the image orthicon.
But let us now return to the film camera. Since the amount of
light is practically unlimited in the projector (for it is a simple
matter to increase the power of the illumination), the iconoscope
is quite well suited, for it has a higher resolving power than many
image orthicons. The film camera contains no lenses and is very
simple compared with the live studio camera. The picture from
the projector is focussed directly on the mosaic by means of the
projection lens and is about four by three inches in size. The tube is
scanned in the same manner as the live camera and is driven by