Conference call circuit

Claim 1

A CONFERENCE CALL CIRCUIT COMPRISING TWO GROUPS OF SUBSCRIBER LINES CONNECTED RESPECTIVELY TO TWO PLURAL CONDUCTOR LINES SO THAT EACH OF SAID PLURAL CONDUCTOR LINES HAVE SUBSTANTIALLY EQUAL IMPEDANCE, A CONSTANT CURRENT AMPLIFIER CONNECTED INTERMEDIATE TO AND IN SERIES WITH SAID PLURAL CONDUCTOR LINES WHEREBY THE IMPEDANCE OF THE SUBSCRIBER LINES CONNECTED TO ONE OF SAID PLURAL CONDUCTOR LINES BALANCES THE IMPEDANCE OF THE SUBSCRIBER LINES CONNECTED TO THE OTHER OF SAID PLURAL CONDUCTOR LINES, AT LEAST ONE TRANSISTOR HAVING EMITTER, BASE AND COLLECTOR ELECTRODES, SAID AMPLIFIER INCLUDING SAID TRANSISTOR CONNECTED AS A COMMON BASE TRANSISTOR AMPLIFIER STAGE, A HYBRID NETWORK HAVING AT LEAST ONE WINDING CONNECTED IN SERIES WITH SAID PLURAL CONDUCTOR LINES, MEANS INCLUDING ANOTHER WINDING OF SAID NETWORK INDUCTIVELY COUPLED TO SAID ONE WINDING FOR APPLYING AN INPUT SIGNAL TO THE EMITTER OF SAID TRANSISTOR, AND MEANS INCLUDING THIRD WINDINGS OF SAID HYBRID NETWORK COUPLED TO THE COLLECTOR OF SAID TRANSISTOR FOR APPLYING AN AMPLIFIED SIGNAL FROM SAID AMPLIFIER THROUGH A MIDPOINT OF SAID ONE WINDING TO SAID PLURAL CONDUCTOR LINES.