DTMF Communication system

Details DTMF Communication system DTMF Communication system

1976-10-01

1978-05-02

Stellar, George G.

Communications: electrical

Land vehicle alarms or indicators

Internal alarm or indicator responsive to a condition of the...

179 84VF, 179 90B, 179 90K, 328 14, 340365S, H04M 1100

Patent

active

040876381

ABSTRACT:
A highly flexible and economical dual tone multiple frequency (DTMF) communication system includes a data input source such as a keyboard; a repertory dialer or electronic memory; an integratable digital encoder which includes a digital sine wave synthesizer; and a transmission unit such as a radio or a connection to a standard utility telephone system. The digital encoder provides a DTMF output signal at standard telephone frequencies in response to input data and includes a predial delay circuit which allows for dial tone delay or transmitter start up after receipt of data and before generation of an output signal, a two second delay circuit providing a two second output signal which may be utilized to prevent shut down between successive number entries and to lock out noise from a microphone or to a speaker and an automatic number insertion (ANI) circuit. When enabled, the automatic number insertion circuit automatically locks out a keyboard or other data source and transmits a 4 or 8 digit number supplied by a ROM before transmitting keyboard information. The ANI number may be used for automatic dialing, as a station identifier preceeding radio transmissions or as a code key enabling access to restricted information. Additional features provide in even further operator convenience.

REFERENCES:
patent: 3820028 (1974-06-01), Thomas
patent: 3860765 (1975-01-01), McCabe et al.
patent: 3932709 (1976-01-01), Hoff et al.
patent: 3970801 (1976-07-01), Ross et al.
patent: 4007459 (1977-02-01), Hagelbarger

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