PROTECTION SWITCHING DEVICE FOR SUBSCRIBER'S LINE INTERFACE CIRCUITS Russian patent published in 1998 - IPC

FIELD: telephone communications. SUBSTANCE: since subscriber's line interface circuits are sensitive to overvoltage often caused by lightning affected subscriber's lines, their operations could be in danger. Overvoltage can be alleviated by means of switching circuits with expensive special-purpose elements and additional circuits. This invention discloses device design in which this is achieved by general-purpose power thyristor, which control electrode voltage or cathode voltage in blocked state or overvoltage in conducting state is compared to reference voltage by means of comparator. If overvoltage is detected subscriber's line interface circuits are switched on when no current runs through control input so that level of blocking thyristor is not reached. Current is supplied again, only if there is no overvoltage in blocked state. EFFECT: decreased cost, possibility of protection of multiple subscriber's line interface circuits. 1 dwg