LINE LOAD RESISTANCE MONITORING CIRCUIT, AND OFFICE POWER FEED DIGITAL SUBSCRIBER CIRCUIT DEVICE

摘要

PROBLEM TO BE SOLVED: To highly precisely detect the abnormality of the line load of a subscriber line without any erroneous detection. SOLUTION: Line load monitoring resistors R9 and R10 are installed in the respective signal lines of subscriber lines in the output part of a feeding power circuit PWR0 and firs and second voltage stabilizing circuits IC0 and IC1 between output terminals. Comparators IC2 and IC4 compare the bridge outputs of the respective voltage stabilizing circuits and the voltage drop of the line load monitoring resistors R9 and R10. IC3 and IC5 detect whether the voltage drop of the line load monitoring resistors R9 and R10 is positive or negative. The increase of the resistance value of the subscriber line is detected by respective comparison results.