Abstract: Apparatus for adapting a standard telephone set for use in an intercom system communicating over the two "extra" conductors of the four-conductor wiring typically provided on the premises of a telephone subscriber. The adapter is inserted between the telephone and the premises wiring. A hold button, intercom signaling button, intercom select switch, and various indicators are provided by the adapter, which provides these features without requiring separate connection to a power source. The hold function automatically releases at the end of a conversation. Indicators warn the user to switch from intercom to central office when an incoming call is present and the intercom is selected. The intercom is usable even when the central office line is out of order.

Abstract: A remote supervisory system operating in conjunction with a telephone company central office to enable monitoring of a subscriber's premises over existing telephone circuits. Auxiliary equipment at the subscriber's premises is coupled to the subscriber's telephone circuit and includes sensors which monitor the condition of the premises. If an abnormal condition occurs at the premises, the condition is sensed by one of the sensors and the equipment, in response thereto, creates a temporary off-hook condition on the circuit, transmits to the central office alarm report signals indicative of the abnormality, and then goes back on-hook. The central office identifies the subscriber as it does in the case of a normal outgoing call, senses the transmitted alarm report signals and stores the signals and subscriber's identity in its memory. The central office may be equipped to initiate a call to a predesignated action center to report the subscriber's identity and nature of the alarm.

Abstract: Responder apparatus enables a telephone subscriber to obtain a status report of the conditions at his premises by placing a telephone call thereto from a remote location. The subscriber dials his telephone number and permits his telephone subset to ring an abnormally large number of times n. The responder apparatus, which is installed at the premises, counts the rings and, upon the nth ring, creates a temporary off-hook condition on the subscriber's line. During the off-hook period, a status reporting unit sends signals over the line to the calling subscriber which are indicative of the conditions at the premises. The signals, which are generated under the control of various sensors at the premises and which may be in the form of coded tones, may indicate that the temperature of the premises is or is not normal, that intrusion has or has not taken place, and numerous other such conditions.

Abstract: Standard four prong, plug-in telephone sets are modified to enable intercommunication among the sets on the subscriber's premises. In a subscriber telephone system including a single central office circuit, only two of the standard four prongs and associated receptacle sockets are used for establishing connection to the central office circuit. In the disclosed system, a local intercom circuit is added to the premises and connects to the remaining two sockets in each receptacle so that each set that is plugged in is also connected to the intercom circuit. The sets are modified to include a line selector switch which enables the talk circuits therein to be switched back and forth between the central office circuit and the intercom circuit. An intercom call signal generator and detector is also added to each set for intercom call signalling over the intercom circuit.