GB1431862A - Public service devices such as parking meters - Google Patents

Abstract

1431862 Alarm system SUSSEX POLICE AUTHORITY 15 May 1974 [15 Feb 1973] 7520/73 Heading G4H A public service device alarm system comprises a radio transmitter and means to cause operation thereof to transmit an alarm signal in response to the sensing of tampering with the device and/or to the application of percussive force thereto. The device could be a parking meter, a lamp post, a telephone coin box, &c. As described, a parking meter incorporates a microswitch 19 and a vibration sensing device 20 which detect removal of the cash box 9 and the application of force to the meter, in response to which a signal 22, 23 is sent via leads 18 to the transmitter circuitry 10. This signal causes a trigger 21 to operate a timer 12 whose outputs enable transmitter 14 and a regulator 25 for, e.g. 1 minute. The regulated output 39 from 25 causes a keying logic circuit 13 to send audio modulating signals to transmitter 14, which transmits a modulated signal 15 to the nearest police station. The modulating signal may consist of bursts of pulses, the number of pulses in each burst serving to identify the transmitting device. Alternatively, the signal may be in the form of an identifying sequence of dots and dashes. The modulated signal 15 may be accompanied by a pilot tone. A description is given of trigger and timing circuits 21, 12 and of logic circuit 13 with reference to Figs. 4 and 5, 6 respectively (not shown).