METHOD FOR SECURITY ALARM Russian patent published in 1997 - IPC

FIELD: automation, in particular, fire and security alarm devices. SUBSTANCE: method involves loop state monitoring by receiving and control unit. When noise is induced, contacts of detectors in loop chat or intruder enters monitored area, pulses of different duration are generated in loop. These signals are subjected to time selection. Final-control unit runs additional analysis of signal about detector operations and its time selection. If duration of signal is greater than 70 ms, then device sends to loop alarm signal which duration results in reception of ALARM signal by receiving and control unit. EFFECT: increased reliability, decreased cost, possibility to use fire alarm circuits as security alarm devices. 2 cl, 1 dwg