Abstract: A telephone alarm system is provided including transmitter and receiver units for interconnection through telephone lines and exchange circuits. In response to an alarm signal, a line circuit in the transmitter unit is operated to an on-line condition and upon receipt of dial tone, a dialing circuit is operated to signal the exchange circuits to apply a ring signal to the receiver unit which responds to establish a completed connection. A request data tone signal is then transmitted from the receiver unit to the transmitter unit and in response, the transmitter unit transmits frequency shift keying signals generated from serial trains of pulses developed by a converter circuit which is controlled from parallel connections to a plurality of output lines of a memory circuit. The memory circuit stores coded word information which uniquely identifies the transmitter unit and also stores information as to the telephone number of the receiver unit.