Multi-frequency tone signaling system

Claim 1

A SIGNALING SYSTEM FOR USE IN AN AUTOMATIC TELEPHONE SWITCHING SYSTEM THAT PROVIDES SUPERVISORY POTENTIALS INDICATING THE PROGRESS OF A CALL THROUGH THE SWITCHING SYSTEM, MEANS FOR TRANSMITTING SWITCH DIRECTING SIGNALS THROUGH SAID SYSTEM VIA TALKING CIRCUITS, SAID SIGNALS APPEARING THE FORM OF A PLURALITY OF MULTI-FREQUENCY TONES, A PLURALITY OF BANDPASS FILTERS TUNED TO SAID SIGNAL FREQUENCIES, MEANS FOR INTERCOUPLING SAID TALKING CIRCUITS WITH SAID PLURALITY OF BANDPASS FILTERS FOR CONTROLLING THE EXTENSION OF SAID TALKING CIRCUITS THROUGH SAID TELEPHONE SYSTEM, SAID MEANS FOR INTERCOUPLING COMPRISING AT LEAST ONE BAND REJECT FILTER TUNED TO REJECT THE FREQUENCY OF AT LEAST ONE OF SAID FREQUENCIES, AND SWITCH MEANS INDIVIDUALLY ASSOCIATED WITH SAID BAND REJECT FILTER FOR SELECTIVELY CONTROLLING THE INSERTION OR REMOVAL OF SAID BAND REJECT FILTER IN SAID MEANS FOR INTERCOUPLING RESPONSIVE TO SAID SUPERVISORY POTENTIALS.