A polarity inversion detection circuit, a complete pole detection circuit, a bell signal detection circuit, and a constant current circuit, a pulse edge detection circuit, a constant current on and off type switching circuit, a pulse pole edge detection circuit, Circuit, control power supply circuit and high voltage detection circuit

摘要

The polarity reversal of the communication line can be detected without malfunction and the detection circuit can be integrated.;The full-wave rectifying circuit 20 rectifies the voltage of the communication line and outputs a voltage of a predetermined polarity. The polarity inversion detection circuit detects the voltage increase edge between the communication lines L1 and L2 using the edge detection circuits 30A and 30B. Each of the edge detecting circuits 30A and 30B is composed of a pseudo differential circuit having the same structure. For example, the edge detecting circuit 30A outputs the trigger current in the short end of the rising edge. The trigger current is given to the constant current ON / OFF type holding circuit 50 via the OR circuit 40, and the constant current ON / OFF type holding circuit 50 is set to maintain and output the polarity inversion information. Reset and return to the standby state.