"TALKING CLOCK."

Auckland Star, Volume LXVII, Issue 106, 6 May 1936, Page 6

"TALKING CLOCK."

LONDON TELEPHONE SERVICE. A demonstration wae given at the London Post Office Research Station recently of/the "talking clock" system, by which telephone subscribers will soon be able, on dialling "TIM," to hear the time announced. The service will be made available to the public on July 1, and will, in the first place, be confined to London. On dialling "TIM" the subscriber -\vjll be connected with the clock in the same way as with the switches at any other exchange, and will be allowed to listen to the time announcement for a period of from 90 to 180 seconds, when tho call will automatically end. The time is announced by the clock at intervals of 10 seconds, and, assuming that tho call is made at 3.10, the announcement will be in the following terms: "At the third stroke it will be 3.10 precisely." There follow the three etrokes, technically known as pips, and the clock goes on to announce: "At the third stroke it will be 3.10 and 10 seconds." The next announcement is for "3.10 and 20 seconds"—and so on.

The clock consists of four glass dtecs rotating on two shafts. On the discs are a number of concentric circular sound tracks which constitute records of the numbers from' 1 to 59, words eucli as "o'clock" which are required in building up the time announcement, and the initial and final parts of the sentence. The words are recorded in much the same way as .speech and music are recorded on the track placed along the edge of a talking cinematograph film. Speech Is reproduced from the discs by focusing a beam of light on to one of the tracks and allowing the light which passes through to fall on to a photo-electric cell, thus producing an electric current which may be amplified by moans such as are employed in talking pictures. As the clock can be checked by. comparison with a signal from Greenwich Observatory only once an hour, the speed of rotation of the discs must not vary by more than one part in 36,000. In order to meet this requirement a novel type of drive has been devised. A pendulum, beating seconds accurately, has fixed to its end a shutter swinging in front of a photoelectric cell. A light is focused on to this shutter, and is so arranged that as the pendulum ewings the light on the photo-electric cell varies hi a regular manner four times a second. The current produced by light shining on this cell is amplified, and finally drives to rotate the clock by means of a eyachrououa motor.