POLARITY INVERSION DETECTION CIRCUIT, SLOW POLARITY INVERSION DETECTION CIRCUIT, BELL SIGNAL DETECTION CIRCUIT, CONSTANT CURRENT CIRCUIT USED FOR THEM, PULSE EDGE DETECTION CIRCUIT, CONSTANT CURRENT ON/OFF SWITCH CIRCUIT, PULSE FALL EDGE DETECTION CIRCUIT, MONOSTABLE MULTIVIBRATOR, PULSE WIDTH EXTENSION CIRCUIT, CONTROL POWER SUPPLY CIRCUIT AND HIGH VOLTAGE DETECTION CIRCUIT

摘要

PROBLEM TO BE SOLVED: To configure a polarity inversion detection circuit as a monolithic IC by configuring an edge detection circuit without the use of a capacitor with a large capacitance. SOLUTION: A full wave rectifier circuit 20 applies full wave rectification to a current flowing to a communication line and provides an output of a voltage with a constant polarity from its positive and its negative terminals. First and second edge detection circuits 30A, 30B detect a polarity inversion edge of a start or restoration signal to provide an edge detection trigger current. A detection signal generating section 40 synthesizes the 1st and 2nd edge detection trigger current to outputs a detection signal denoting the provision of a start signal or a restoration signal to a terminal. A holding circuit 50 holds polarity inversion information set by the detection signal and outputs it. Since no capacitor is employed for the polarity inversion edge detection circuit, the circuitry is proper to circuit integration and no current is supplied except edge detection, then the configuration of low power consumption is attained.