GB1257549A - - Google Patents

Abstract

1,257,549. Watchman's checking system. WORMALD BROS. INDUSTRIES Ltd. 19 Dec., 1969, No. 62105/69. Heading G4T. For checking the correct sequence of a watchman's round, a portable device carried by the watchman comprises a chain of switching circuits which are actuable sequentially by respective activating devices that are situated one each at an outstation on the round; the portable device provides means for signalling the correctness or incorrectness of the round. Watchman's round.-For a round having eight outstations and a master (final) station, the portable device (see Fig. 1) provides eight switching circuits, each comprising a pair of normally off transistors Q1, Q2 and a receiving coil L1-L8. At the beginning of a round, a switch SW1 is closed to activate a pair of pulse generators 2, 3 having an actuating transmitter coil TB and an " incorrect " signal coil TC respectively. A third pulse generator 4 having a " correct " signal coil TD remains unactivated. The coils L1-L8, TD, TC, TB are mounted in a matrix configuration on a rectangular faceplate. Each activating device (not disclosed in detail) located at an outstation possesses a similar faceplate carrying a first and a second coil that correspond in position to the actuating transmitter coil TB and one of the receiving coils L1-L8 respectively, when the faceplates are mated. At the first outstation, the pulsing of the actuating transmitter coil TB of the portable device (Fig. 1) is picked up by said first coil, which activates the second coil (by means not disclosed) to pulse the receiving coil L1 of the portable device and so switch the first pair of transistors Q1, Q2 hard on. At the second outstation the receiving coil L2 is similarly pulsed to switch on the second switching circuit. The supply potential to the emitter of transistor Q2 of switching circuits two-eight is provided by the previous stage when in an " on " state, so that the stages can only be activated sequentially and if every outstation on the round is visited. The state of the eighth stage therefore represents the correctness of the watchman's round; when this stage is on, it activates the third pulse generator 4 to give a " correct " signal in coil TD, and deactivates the second pulse generator 3 to remove the " incorrect " signal in coil TC. Operation at master station.-The faceplate of the activating device at the master station supports coils RB, RC, RD, TA (Fig. 2) positioned to receive signals from respective coils TB, TC, TD (Fig. 1) and to transmit a resetting signal to a coil RA of the portable device. The actuating transmitter coil TB pulses sensor coil RB (Fig. 2) to switch transistor Q8, Q9 hard on to apply a positive potential to one terminal each of two relays RL1, RL2. If coil TD (Fig. 1) is transmitting pulses to sensor coil RD (Fig. 2) the corresponding transistors Q6, Q7 will switch hard on to apply a negative potential to the second terminal of relay RL2, through relay contacts RL1-2, to indicate a " correct " round. The appropriate contacts then switch over: (a) RL2-1 to " lock " relay RL2 to the negative supply terminal; (b) RL2-2 to isolate relay RL1; and (c) RL2-3 to activate the resetting coil TA through a delay C1, R6 that allows the relay RL2 to " lock-on " before resetting pulses are emitted. The reset coil RA in the portable device (Fig. 1) then switches a transistor Q1 hard on to short the base/emitter junction of transistor Q1 in the first stage switching circuit, and so successively return all the switching circuits and pulse -generators to their initial states. The activating device (Fig. 2) at the master station is deactivated when the portable device (Fig. 1) is removed. If, alternatively, coil TC (Fig. 1) is transmitting pulses to sensor coil RC (Fig. 2), the relay RL1 is energized, to indicate an " incorrect " round, and resetting is similarly instigated. The master outstation may be connected to'a central supervisory station by telephone cable. A timing device may be incorporated in the portable device to limit the time of the round, or at the master and at an outstation to provide an alarm if the watchman's round is delayed. Wired plugs may be used with the portable unit to vary the sequence of the round-; a meter can be employed to indicate the final outstation visited, or to measure the battery current drawn, as this increases -for each outstation visited that has caused a switching effect. The coils at the faceplates may be wound coaxially, and audio tones used for transmission. K.J. flip-flops, or logic gates may be used as alternative switching circuits.