Telephone line circuit

Claim 1

SUPERVISORY EQUIPMENT FOR A TELEPHONE SYSTEM COMPRISING A PLURALITY OF MULTI-PARTY LINE CIRCUITS EACH RESPECTIVELY CONNECTED TO ONE OF A PLURALITY OF TELEPHONE LINES, A RESPECTIVE SUPERVISORY MAGNETIC CORE COUPLED TO THE TIP AND RING LINE CONDUCTORS IN EACH OF SAID LINE CIRCUITS, MEANS COUPLED TO ALL OF SAID CORES FOR MAINTAINING THE MAGNETIZATION OF SAID CORES IN A FIRST STATE, CONTROL MEANS FOR SELECTIVELY TRANSMITTING CONTROL SIGNALS TO SAID LINE CIRCUITS, MEANS IN EACH OF SAID LINE CIRCUITS RESPONSIVE TO FIRST CONTROL SIGNALS FOR APPLYING RINGING CURRENT TO ONE OF THE RESPECTIVE TIP AND RING CONDUCTORS, MEANS FOR EXTENDING SAID RINGING CURRENT TO THE OTHER OF SAID CONDUCTORS RESPONSIVE TO AN ANSWER BY THE CALLED PARTY TO SWITCH THE MAGNETIZATION OF THE RESPECTIVE CORE TO A SECOND STATE, MEANS IN EACH OF SAID LINE CIRCUITS COUPLED TO THE RESPECTIVE CORE FOR DETECTING THE SWITING OF THE CORE MAGNETIZATION TO DETERMINE THAT THE CALLED PARTY HAS ANSWERED, AND MEANS IN SAID CONTROL MEANS FOR SELECTIVELY INTERROGATING SAID DETECTING MEANS.