CLOCK No. 70
|P.O. ENGINEERING DEPT.
Issue 1, 4.11.58
ELECTRICAL CLOCKS - PULSE TYPE
The actual 24-hour pulse is transmitted via springs S3 and S4 which close a few minutes before 1 p.m. and open a few minutes after 1 p.m. The hourly pulses and the 24-hour pulse are transmitted on separate outlets from the clock. The clock was designed for use where routiner docket control equipment, subscriber trunk dialling meter-pulse generating equipment, or disputed accounts equipment is installed. Normally the clock is driven by 30 second pulses derived from the master clock (Clock No. 36) but it will operate to `interrupted earth’ (075 second on, 0.75 second off) for resetting the clock (see par. 4).
Fixed to the wheel W is an index disk Dl, carrying on its periphery a metal pin. During the revolution of the wheel and disk this pin short-circuits springs S 1 and S2 at every hour precisely and connects earth to the
1 hour pulse lead. The next 30 second pulse removes the short-circuit from these springs and the pulse on the
1 hour pulse lead ceases. To prevent false pulses being transmitted due to backlash in the clock gearing, springs S 1
and S2 are of different lengths. The wheel W drives, by means of a 24 to 1 reduction gear, the
24 hour disk D2 which is recessed on its periphery at a point marked 1 p.m. Two springs S3 and S4 are kept open, until one of the springs drops into the recess a few minutes before 1 p.m. The
closing of the springs prepares the clock to transmit the 24 hour pulse. Springs S3 and S4 open a few
minutes after 1 p.m.
4. Advancing and retarding the clock
Last revised: February 21, 2022