Abstract: Telephone apparatus for installation at a subscriber station to enable call forward operation as used in combination with the standard subscriber facilities. The unit includes ring detection and call forward programming circuitry. The call forward programming circuitry includes apparatus connected to the subscriber line and effective to dial a call forwarding access code and designated forwarding telephone number from a programmable storage. The ring detection circuitry provides for automatic actuation of the call forward program unit in the event of failure to actuate or energize manually.

Abstract: A communication system for combining telephone service with hands-free talk-back intercom service is disclosed. The telephone service includes a telephone exchange network having an outside trunk, an internal trunk, and a device for switching the telephones within the system between either the outside trunk or the internal trunk in response to appropriate signals from the telephones. The intercom network generally includes a main distribution station associated with various telephones and transducers. Various embodiments of the system, having differing numbers of the above elements, are disclosed.

Abstract: A hands-free talk-back two-way intercommunication system is disclosed. The system includes a plurality of local stations connected to a main distribution station. Also connected to the main distribution station may be a direct station selector. At least one of the local stations includes a telephone and at least one of the other local stations includes a transducer element. The telephone and the transducer element may be connected in communication with each other through the main distribution station which includes a listen/talk channel controlling member, a call monitoring member and a station selecting member. The listen/talk channel controlling member includes apparatus for adjusting the balance between the listen and talk channels. The channel controlling member also includes apparatus for providing a notification signal to any transducer member which is addressed by the telephone.

Abstract: A safety circuit for protective operation at the interface between certain customer premises telephone installations and the external telephone distribution lines. The protection circuit includes a means for discriminating any voltages of sufficient magnitude having a frequency at or near 60 Hz., and upon such detection, a reactance means is responsive to open the connection between the premises telephone installation and the external telephone distribution line.

Abstract: An interconnect circuit arrangement for patching a simplex or half-duplex radio network into a standard telephone system. It includes means for sending beep tones to the parties at the end of each message so that they can readily recognize when each is supposed to talk. The tones are sent automatically when the party on the telephone system concludes his messages, and under manual control of the party at the radio end when he concludes his. Special access codes are provided to prevent unauthorized access to the radio system and to set the circuit for special functions. Various override features are included to facilitate operation and avoid time delays that have heretofore tended to hinder conversations in VOX simplex and half-duplex radio systems.