Call and release signal detector for PBX - has recognition circuit with full-wave rectifier controlling opto-electronic coupler

摘要

The detector sense 1.f. ccall signals and d.c. release signals and contains a recognition circuit having a full-wave rectifier that controls an opto-electronic coupler. The recognition on circuit is connected in the line's quiescent state between the two speech wires. When the line is engaged the recognition circuit is connected into one of the two wires. The recognition circuit contains an electronic self-regulating shunt which produces a constant voltage drop independent of the magnitude of the current flowing. The voltage drop is adequate for driving the opto-electronic coupler. The advantage lies in the detector's dual purpose no modifications are needed.