Party line subscriber identifier

Claim 1

A TELEPHONE SYSTEM COMPRISING AN EXCHANGE, A PARTY LINE CONNECTED TO SAID EXCHANGE, A PARTY LINE SUBSCRIBER STATION CONNECTED TO SAID PARTY LINE AND HAVING DIAL CONTACTS, SWITCH MEANS AT SAID STATION FOR DIRECTLY CONNECTING SAID DIAL CONTACTS ACROSS SAID LINE, WHEREBY SUCCESSIVE OPENING OF SAID DIAL CONTACTS PRODUCES DIAL PULSES ON SAID LINE, AN OSCILLATOR AT SAID STATION DIRECTLY CONNECTED ACROSS SAID DIAL CONTACTS AND ARRANGED TO OSCILLATE AT A PREDETERMINED FREQUENCY ONLY WHEN SAID CONTACTS ARE OPEN AND CONNECTED ACROSS SAID LINE AND SAID OSCILLATOR IS THUS DIRECTLY CONNECTED TO SAID LINE, FREQUENCY SIGNAL SENSING MEANS AT SAID EXCHANGE TUNED TO SAID PREDETERMINED FREQUENCY, AND MEANS AT SAID EXCHANGE COUPLED TO SAID PARTY LINE AND RESPONSIVE TO EACH OPENING OF SAID DIAL CONTACTS WHEN SAID DIAL CONTACTS ARE DIRECTLY CONNECTED TO SAID LINE FOR CONNECTING SAID FREQUENCY SIGNAL SENSING MEANS TO SAID LINE, SAID CONNECTING MEANS HAVING A DELAY IN OPERATING SUFFICIENT FOR SAID OSCILLATOR TO PRODUCE A STEADY OSCILLATION AT EACH OPENING OF SAID DIAL CONTACTS AND FOR THE TRANSIENT PULSE INCIDENT TO THE OPENING OF SAID DIAL CONTACTS TO DISSIPATE BEFORE SAID FREQUENCY SIGNAL SENSING MEANS IS CONNECTED TO SAID PARTY LINE.