Telephone signalling circuits

Claim 1

A TELEPHONE SIGNALLING ARRANGEMENT COMPRISING AN INPUT LOOP HAVING MEANS TO GENERATE RINGING SIGNALS, AN OUTPUT LOOP, AND A SIGNAL REPEATING MEANS CONNECTED BETWEEN SAID INPUT LOOP AND SAID OUTPUT LOOP FOR REPEATING SAID RINGING SIGNALS, SAID SIGNAL REPEATING MEANS COMPRISING: (A) A TRANSFORMER HAVING A PRIMARY AND A SECONDARY WINDING, THE PRIMARY WINDING OF SAID TRANSFORMER BEING ENERGIZABLE IN RESPONSE TO THE RINGING SIGNALS FROM THE INPUT LOOP; (B) A VOLTAGE SOURCE CONNECTED TO THE OUTPUT LOOP; (C) A SOURCE OF RINGING CURRENT CONNECTED TO THE OUTPUT LOOP; AND (D) TRANSISTOR SWITCHING MEANS OPERABLE IN RESPONSE TO THE POTENTIAL INDUCED IN THE SECONDARY WINDING OF SAID TRANSFORMER BY ITS PRIMARY WINDING FOR REMOVING SAID VOLTAGE SOURCE FROM THE OUTPUT LOOP AND FOR CONNECTING SAID SOURCE OF RINGING CURRENT THERETO, SAID SWITCHING MEANS INCLUDING A NORMALLY CONDUCTING TRANSISTOR CONNECTING SAID VOLTAGE SOURCE TO THE OUTPUT LOOP AND A NORMALLY NONCONDUCTING TRANSISTOR CONNECTING THE SOURCE OF RINGING CURRENT TO THE OUTPUT LOOP, THE TRANSISTORS BEING REVERSIBLE TO THEIR OPPOSITE CONDUCTIVITIES IN RESPONSE TO ENERGIZATION OF THE TRANSFORMER UPON APPLICATION OF A RINGING SIGNAL FROM THE INPUT LOOP.