Distributed fire alarm network with centralised control - subjects incoming signals to repeated threshold comparative test and uses logic circuits prior to alarm activation

摘要

The distributed fire alarm network uses a number of multiplexed two line cables each serving an array of one or more parallel transducers, with a centralised control network in which the incoming transducer signals are subjected to a repeated threshold comparison test before a fire alarm is raised. A number of two wire cables (L1, L2, L3) each serve an array of parallel transducers (D) typically of the smoke detection type. Each cable feeds signals at the central control to an interface network (A1, A2, A3) and these feed a common processing network (36) in a multiplexed fashion. The interface and common network contain storage (28, 58, 60, 38) threshold detection (24, 62, 46) integration (34) and logic circuits together with a clock timer (48) and these together subject any incoming signal, which is represented by a line current increase to a sequency threshold checks, typically 10 in number, before an alarm is raised and a fire suppression control circuit (70) activated.