Patent GB-730570-A (GB)
Title: Improvements in programme timing devices
Inventor: WILDING FREDERICK ANDREW
IPC: G07C1/20
Filed: 1952-03-20
Abstract: 730,570. Time-alarm signals. TELEPHONE RENTALS, Ltd. March 20,1952, No. 7256/52. Class 118 (2). [Also in Group XIX] A signalling system comprises a device giving a signal at the time an operation should be initiated, the operation being one of a plurality of operations which have to be. performed in succession with a given period of time, each having to be initiated, performed and ended within its own sub-period within the given period of time. As applied to a watchman's control system, wherein the watchman is required to perform the operation of patrolling premises once within each two-hour  period between 6 p.m. and 8 a.m., a signal is given to indicate that a patrol should begin at a time in each two-hour period which depends upon the lapse of time between a random event, namely the end of the last patrol and one of a succession of arbitrarily-determined impulses occurring within that same two hour period. If a patrol takes forty-five minutes and a minimum rest period of ten minutes is to be ensured a patrol may begin at any time within the first sixty-five minutes of a two-hour period and the signal is given at 5n minutes after the beginning of the two-hour period where n is any whole number from 0 to 13 depending on the said lapse of time. A suitable circuit is shown in Fig. 2 comprising three relays P, R, M, three sources of electric impulses c, 5m, m at twohourly, 5-minute and minute intervals respectively, a key-operated switch SD<SP>1</SP>, a uniselector having a bank of twenty-five contacts and a wiper RS<SP>1</SP>, a driving magnet RSDM and interrupting contacts rsdm for providing selfdrive and an automatic interrupter INT having contacts int. In operation, assuming the wiper RS<SP>1</SP> is resting on contact 5 as shown, when a two-hourly impulse closes contact c the relay P is energized and operates switches p<SP>1</SP>, p<SP>2</SP>, p<SP>3</SP>, p<SP>4</SP>. p<SP>1</SP> closes a holding circuit, p2 enables the next 5-minute impulse to energize the driving magnet RSDM which causes the wiper to advance to the next contact and so on each 5 minutes until the wiper reaches the fourteenth contact and closes a circuit SC through p3 to give the signal for the patrol to begin. After the next 5-minute impulse the wiper rests on the first of ten contacts connected together and to the interrupter contacts rsdm and self-drive action moves the wiper rapidly to the last contact 25 to complete a circuit through p4 and a resistor RP which short-circuits relay P and releases it, the return of p<SP>4</SP> to normal sets up further self-drive to home the wiper RS<SP>1</SP> to contact 1 where it remains until, at the end of his patrol, the watchman closes switch SD and energizes relay R to close contacts r<SP>1</SP> in a holding circuit and r<SP>2</SP> in a circuit through the interrupter INT which operates at a frequency of one per second to deliver impulses to the magnet RSDM thus stepping on the wiper RS<SP>1</SP> from contact 1 to 15 when it is rapidly homed to 1 to repeat the process until the next minute impulse at m energizes relay M to open contacts m<SP>1</SP> and release relay R to open contacts r<SP>2</SP>, break the interrupter INT circuit and leave the wiper RS<SP>1</SP> at rest on one of the first fourteen contacts, e.g. on the contact five as shown. The random element may be introduced by making the time for a patrol to begin depend upon the lapse of time between the reaching of a stage in and the end of the preceding patrol. Specification 602,462 is referred to.