Party line sub-station

Claim 1

A PARTY LINE TELEPHONE SYSTEM COMPRISING A PLURALITY OF SUB-STATIONS CONNECTED IN PARALLEL, A COMMON SUPPLY OF VOLTAGE OF PREDETERMINED MAGNITUDE FOR APPLYING RINGING AND TALKING CURRENTS TO SAID PLURALITY OF SUB-STATIONS; EACH OF SAID SUB-STATIONS INCLUDING A TRANSMITTER AND A RECEIVER AND AN IMPEDANCE DEVICE IN SERIES WITH SAID TRANSMITTER AND RECEIVER, SAID IMPEDANCE DEVICE BEING CHARACTERIZED BY A NORMALLY HIGH LEVEL OF IMPEDANCE WHICH IMMEDIATELY DROPS TO A LOW IMPEDANCE LEVEL WITH A CORRESPONDING DECREASE IN VOLTAGE ACROSS SAID DEVICE SUBSTANTIALLY BELOW SAID PREDETERMINED MAGNITUDE WHEN SAID DEVICE IS SUBJECTED TO SAID VOLTAGE OF PREDETERMINED MAGNITUDE, A SUB-STATION HAND-SET HOOK SWITCH IN SERIES WITH EACH OF SAID IMPEDANCE DEVICES, WHEREBY WHEN ONE OF SAID HOOK SWITCHES IS CLOSED SAID VOLTAGE OF PREDETERMINED MAGNITUDE IS APPLIED TO THE ASSOCIATED IMPEDANCE DEVICE FROM SAID COMMON VOLTAGE SUPPLY, THEREBY CAUSING THE IMPEDANCE OF SAID ASSOCIATED IMPEDANCE DEVICE TO DROP TO SAID LOW LEVEL WITH A CORRESPONDING DECREASE IN VOLTAGE THEREACROSS, THE IMPEDANCE DEVICES IN THE OTHER SUB-STATIONS OF SAID PARTY LINE REMAINING IN THE NORMAL HIGH LEVEL CONDITION OF IMPEDANCE.