CONNECTING CIRCUIT FOR A TELEPHONE LINE

摘要

1 PHN. 9457. Connecting circuit for a telephone line comprising a pair of amplifiers whose outputs are connected to the one and to the other wire of the telephone line, respectively. Longitudinal currents which are induced in the telephone line and may negatively affect the proper functioning of the connecting circuit constitute a problem. The connecting circuit uses four current detection circuits for separately detecting the positive and negative currents in the wires of the telephone line. These separately detected currents are processed so, that the desired operation of the connecting circuit is maintained even in the presence of longitudinal currents, which exceed the loop currents. The circuit is used for the connection of subscriber's line to automatic telephone exchanges.