Patent GB-899192-A (GB)
Title: Electrical signalling apparatus
Inventor: BEMIS PHILO SCOVEL
IPC: G08B26/00
Filed: 1960-06-03
Abstract: 899,192. Electric alarm systems. AMERICAN DISTRICT TELEGRAPH CO. June 3, 1960, No. 19798/60. Class 118. In an alarm system, particularly one for burglary detection, each subscriber is connected to a corresponding line terminal unit at an intermediate station, the reception of a signal by a unit causing a line-finder to hunt for the calling line and connect it to a translator, which in response to the condition of the unit causes the transmission over a common link to the central station of signals indicative of the condition at the subscriber's premises and the identity of the subscriber concerned. Setting-up procedure.-In the day condition relay LTC of the line terminal unit (Fig. 4) is operated and connects negative battery to the subscriber's apparatus (Fig. 3) via conductor DW1, the resulting current flowing in day protection circuits 57 and 68 via rectifier 78 and relay SSA, which relay remains unoperated. Opening of this circuit results in operation of the centre-stable polarized relay LTA (Fig. 4) thus initiating an alarm by grounding conductor 73. Before closing his premises the subscriber checks that the reading of the meter 80 in respect of the current flowing in the full protection circuit via resistor 63 is of the correct value, checking the protection devices if it is not. He then opens the exit door, operates the delayed action switch 82, and closes the door. Closure of switch 82 shunts out resistor 79 and relay SSA operates, followed by LTA (Fig. 4) which energizes LTD and LTE. The resulting grounding of the start terminal (Fig. 4) energizes the stepping coil 104 of the line-finder (Fig. 5) which hunts for the calling line unit, indicated by absence of ground on its stop bank contact, and connects the line terminal unit (Fig. 4) to the translator (Fig. 6). The conditions of the LTD, LTC, and LTB relays are read by relays W, X and Y, and in this case, with LTD and LTC energized and LTB unenergized, W and X are unoperated and Y is operated. Relay P comes up with delay and ground is extended over conductor 151 to the " closing " terminal C (Fig. 6), thus initiating the sending of a " closing " signal in respect of the subscriber (see below) to the central station. The time of closing is then compared with the scheduled closing time either automatically or by an operator, the requisite action being taken if the times do not agree within preset limits. The ground on 151 also brings up relay C which applies +24 volts to the " C operate" terminal (Fig. 4) to bring down LTC, grounds the " B operate " terminal to operate LTB, and energizes Q (Fig. 6) which releases P. The energization of LTB connects + 24 volts over DW1 in place of the - 24 volts, the reversal of current releasing SSA (Fig. 3) whereupon LTA restores, followed by LTD, thus operating W (Fig. 6). The release of the translator is effected by a reset signal from the central station energizing relay RC which brings up Z. The + 24 volts is thus removed from the line-finder " release " terminal (Fig. 5) and is applied to the " E operate " terminal to bring down the relay LTE. The resulting grounding of the line-finder " stop " terminal operates LFR (Fig. 5) which removes ground from the S terminal (Fig. 6) whereupon C releases followed by Q and Z, and the line finder homes. The line terminal unit concerned is now in its night condition with LTB only operated. Alarm operation.-In response to either a break or a ground in a protection device LTA (Fig. 4) is operated, followed by LTD and LTE. The line-finder associates the translator with the line unit as before, and W is unoperated while X and Y are operated. The operation of P, which follows, extends ground to " alarm " terminal A and brings up relay A, which grounds the " C operate " lead to energize LTC, and applies - 24 volts to the " B operate " lead to release LTB thus reversing the polarity on DW1, so that SSA falls away if previously operated. LTA releases, followed by LTD and the line unit is then in its day condition. Relay A also brings up Q whereupon P is released, and on the operation of RC from the central station, Z comes up as before, LTE is released followed by LFR, A, Q and Z and the line-finder is homed. Momentary break or ground.-Should this occur during the night condition, LTA, LTD and LTE come up but the first two relays fall back at the end of the momentary break or ground, leaving LTB and LTE energized. The translator is connected up as usual and W and X are operated, P then extending ground to terminal M and relay M. Q comes up and releases P and the condition of LTB and LTC remains unchanged. Operation of RC initiates release of the translator as described above, LTE being de-energized and the line-finder homed. The line unit thus resumes the night condition. Fault conditions at closure.-If the premises are closed with a fault condition on, SSA (Fig. 3) remains up when the polarity on DW1 is reversed if the fault is a ground or cross, and LTA remains up, although SSA is down, if it is an open circuit. In either ease relays LTA, LTB, LTD and LTE are energized and the line unit is still connected to the translator with relays C, X and Q operated. Ground is thus extended to the " trouble " terminal T and to relay T. The operation of T brings down C and maintains Q; LTC is maintained down and LTB is released. With LTC and LTB both down no power is applied to DW1 so that SSA, LTA and LTD are released. Release of the translator results in the restoration of LTE and with all the line unit relays down the unit is in the disconnect condition. The central station sends a maintenance man to the subscriber's premises to clear the trouble whereafter the central station operator dials, with dial 132 (Fig. 7), the required number to set the selector (Fig. 8) to the line concerned, operates switch KB to the night position and switch KO to the operate position. The relay LTB in the line unit is thus operated and the unit restored to the night condition, wherafter the unit is released and the selector homed. Opening premises.-The line unit is conditioned for opening at a scheduled time by dialling of the line number and the setting of KO to " operate " and KC to " opening," thus operating LTC in the line unit. Opening of the premises brings up SSA followed by LTA, LTD and LTE, the line finder connects up the translator and X, Y and Z remain down. P thus extends ground to " opening " terminal O and relay O. Q comes up to maintain LTC operated, and O brings down LTB to reverse the polarity on DW1, thus releasing SSA, LTA and LTD, and the unit is restored to the day condition. Testing.-Operation of KDN (Fig. 7) to its lower position and KTN and KL to their upper, applies +45 volts to DW1. If the protection circuit is in order, SSA comes up and an alarm signal is sent; if not, momentary unbalance of LTA sends a " momentary " signal. In response to the alarm signal the translator transfers the unit to the day condition, whereupon the operator resets it to the night condition. The " momentary " signals initiates action to clear the fault. Emergency operation.-The provision of lamps at the intermediate station translator terminals allows this station to be operated as a manned station should communication to the central station be interrupted. Transmission of signals to central station.- This is effected by tone signalling over a common pair, one tone being allotted to each subscriber and being transmitted when the linefinder is set to the corresponding line unit, and one further tone to each of the L, M, A, C, O, T terminals of Fig. 6 and being sent when the respective terminals are grounded. Automatic operation.-The receipt of all signals at the central station is recorded and they are compared with the normal schedule, punched card apparatus being employed. If openings and closings take place at their normal times no further action is taken, but if they do not, the operator is informed. Apparatus for automatic operation is described with reference to Figs. 12 to 14 (not shown). Specifications 391,496, 566,594, 566,964 and U.S.A. Specification 2,062,118 are referred to.