Working voltage monitor for selector banks in telephone exchange - assigns comparator to each voltage with outputs switched together for unit able to produce alarm signal

摘要

Four comparators (K1,K2,K3,K4) are used to monitor positive working voltages (+U1,+U2,+U3,+U4) and a further four comparators (K5,K6,K7,K8) monitor negative working voltages (-U5,-U6,-U7,-U8). The comparators (K1...K8) compare all working voltages with reference voltages (Ur1,Ur3) that have been derived from a single reference source (REF). Comparator outputs are commoned together and trigger an alarm in the output unit (A) should an over or under voltage condition occur. Low pass filters (TP1...TP8) ar eused on all working voltage inputs to suppress l.f. noise. A coupling network (MKW) is used to maintain a constant comparator hysteresis switching level, independent of the working and supply voltages, when response threshold of the comparators (K1...K8) are set up using the input resistors (R1...R8). USE/ADVANTAGE - Circuit can be easily formed as modules. Comparator response threshold level determined by single input resistor.