Line circuit for telephone system

Claim 1

A CIRCUIT IN A TELEPHONE SYSTEM FOR CONNECTING A CALLING SUBSCRIBER''S WIRES TO A LINE CIRCUIT, COMPRISING A PAIR OF SWITCHING DIODES CONNECTED RESPECTIVELY TO THE WIRES OF A SUBSCRIBER''S LINE, AND SERIALLY IN A LOOP THROUGH THE SUBSCRIBER''S TELEPHONE, MEANS FOR ENERGIZING SAID LOOP SO THAT WHEN THE SUBSCRIBER LIFTS HIS HANDSET CURRENT FLOWS IN THE LOOP, A LINE FINDER RELAYS A CALL DETECTOR CIRCUIT COUPLED TO SAID LOOP AND INCLUDING MEANS OPERATIVE IN RESPONSE TO CURRENT FLOWING IN SAID LOOP FOR OPERATING SAID LINE FINDER RELAY, A LINE FINDER FOR EACH OF THE SUBSCRIBER''S WIRES RESPONSIVE TO THE OPERATION OF SAID LINE FINDER RELAY FOR DETECTING THE CALLING SUBSCRIBER, A LINK CIRCUIT HAVING NORMALLY OPEN CONTACTS CONNECTED TO SAID LINE FINDERS, A TEST CIRCUIT CONNECTED TO ONE OF SAID LINE FINDERS AND OPERATIVE IN RESPONSE TO THE CURRENT FLOWING IN SAID LOOP WHEN SAID LINE FINDER DETECTS A CALLING SUBSCRIBER LINE, SAID TEST CIRCUIT IN ITS OPERATING CONDITION INCLUDING A FIRST MEANS FOR RENDERING INOPERATIVE SAID MEANS OPERATING SAID LINE FINDER RELAY, A SECOND MEANS FOR CLOSING SAID NORMALLY OPEN CONTACTS IN SAID LINK CIRCUIT AND FOR OPENING SAID LOOP, WHEREBY SAID SUBSCRIBER WIRES ARE CONNECTED TO SAID LINK CIRCUIT AND SAID LINE CIRCUIT IS DISCONNECTED FROM THE TALKING WIRES.