Interoffice signaling system employing selected ones of the touch-tone telephone frequencies for establishing interoffice connections

Claim 1

An interoffice signaling network comprised of a plurality of offices which include means for establishing connections to subscribers serviced by the offices as well as connections with other offices in the network, wherein the terminating equipment for each subscriber is comprised of Touch-Tone type telephones capable of generating a plurality of signals of predetermined frequencies wherein said signals all lie within a predetermined frequency range: each of said offices being comprised of outgoing trunks, incoming trunks and a switch matrix for establishing connections between a subscriber telephone and an outgoing trunk and for establishing connections between a called telephone and an incoming trunk; a register for receiving selection signals from a calling subscriber serviced by the office of said calling subscriber to establish a connection with the appropriate office servicing the called subscriber; a sending circuit in each office for transmitting selection signals to the office servicing the called subscriber, said sending circuit being adapted to generate a plurality of signals which are identical to selected ones of the signals capable of being generated of said Touch-Tone telephones; a receiving register in each office for receiving selection signals to operate the switch matrix of its associated office to establish the telephone link with the desired called subscriber.