1976-04-30
1977-09-27
Robinson, Thomas A.
179 2A, H04M 1104
Patent
active
040513270
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. The dialing circuit is also controlled from the memory circuit and includes a counter which counts clock pulses according to bit information supplied in parallel word groups from the memory. The receiver unit responds to the frequency shift keying signals to develop serial trains of pulses which are applied to a converter circuit operative to develop signals applied in parallel to a teleprinter or the like to display the code work unique to the transmitter unit. Circuits are provided in the units for performing various functions including redialing if no dial tone is detected, re-transmission of the data request tone signal if a parity check in the receiver unit is not satisfactory, re-transmission of data and for causing each unit to go off-line after a predetermined time interval.
REFERENCES:
patent: 3233232 (1966-02-01), Brennon
patent: 3702902 (1972-11-01), Willis
patent: 3842208 (1974-10-01), Paraskevakos
Pan-X Corporation
Robinson Thomas A.
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