GB1167142A - Alarm Systems. - Google Patents

Abstract

1,167,142. Alarm systems. A. G. HOOD, and J. R. THOMAS, [trading as TAYSIDE ELECTRONICS]. 20 Sept., 1966 [31 Aug., 1965], No. 37238/65. Heading G4N. An alarm system comprises a button microphone 10 responsive to shock waves and connected in circuit with a remote control unit 15 which incorporates a D.C. power supply 11, an amplifier 12, a switching device 13, an alarm bell circuit 14 and sensitivity adjustment means. The sensitivity may be set by adjusting the gain of amplifier 12 or by attenuating the signal from microphone 10. In modifications the alarm is visual, or audible and visual, and it may be intermittent or continuous. The microphone is attached, e.g. by screwing to a pane of glass or other surface of the article or vehicle to be protected. Switching device ] 3 may be a bi-stable switch such as an Eccles-Jordan bi-stable flip-flop, or a latching relay or a silicon (gate) controlled switch. A transistor operating as a switch or a circuit incorporating a thyratron may also be used. The control circuit may be provided with a reverse biased thyristor or a timing relay so that the alarm signal is cancelled after a predetermined time. In a modification, Fig. 2 (not shown), a transducer (10) incorporates a transmitter (17) and the control circuit incorporates a receiver (18) operable on receipt of a signal from the transmitter (17) to trigger alarm device (14). The transmitter may use radio waves, ultra-sonic sound waves or a light beam. A number of transducers may be employed to operate a single alarm, an indicator being incorporated in the control circuit to show which transducer has caused actuation of the alarm.