GB693630A - Improved burglar alarm system - Google Patents

Abstract

693,630. Burglar alarm systems PRICE, A. B., and McKECHNIE, A. Aug. 17, 1951 [May 17, 1950], No. 12340/50. Class 118 (i). A burglar alarm system comprises a closed circuit detecting device and an open circuit detecting device, each associated with a relay, and a control relay, which are connected in a particular circuit arrangement whereby the control relay prepares the circuit of the open-circuit and closed circuit relays so that disturbance of either of the detecting devices causes an alarm to be operated. The Figure shows an alarm system in which the opening of normally closed contacts CC, or the closing of normally open contacts OC, both being contained in burglar detecting devices, causes an alarm WD to be operated. In setting the system, switch IS is closed to operate relays E/1 and F/1 to light lamps L connected across the main power supply. Remote control switch RCS is also closed to operate control relay C/2, which first closes contact Cl to operate relay A/3 and later closes contact C2 to prepare the circuit of relay B/4. Contact A3 releases relays E/1 and F/1 so that lamps L go out. If a burglar opens one of the contacts CC relay A' releases to operate relay B/4. The lamps L light and contact B3 operates alarm WD from a separate battery, which contact B2 holds relay C/2 operated even if the burglar cuts the circuit of the switch RCS. If the burglar closes contact OC, relay B/4 operates to energize the alarm. The alarm may. be discontinued by opening switch RCS and shorting the contacts CC with plug SP. Lamps L are switched off by opening switch IS. A bandit alarm switch BA is also provided for use when the normal burglar alarm is not operative. Relay D<SP>2</SP> is normally operated from transformer T to provide the system with power from the supply mains, but if these fail contacts D1, D2 substitute a battery PB1 as the power supply.