Multifrequency signal receiver with digital tone receiver

Details Multifrequency signal receiver with digital tone receiver Multifrequency signal receiver with digital tone receiver

1975-12-04

1977-05-03

Cooper, William C.

H04M 150

Patent

active

040216209

ABSTRACT:
A converter, for converting a dual-tone multi-frequency (DTMF) signal produced by a TOUCH-TONE telephone to a 2-out-of-7 coded representation of the "dialed" number, includes an oscillator having a frequency much higher than the frequencies of the tones, a high band circuit for high band tone frequencies, and a low band circuit for low band tone frequencies. Each circuit includes a filter for passing the respective band of tone frequencies from an input terminal, a limiter for translating a received tone sine wave passed by the filter to a corresponding square wave, a counter, a switch enabled by the square wave output of the limiter for coupling the output of the oscillator to the input of the counter during a cycle of the square wave from the limiter, and a decoder for translating the resulting count in the counter to a signal on an output line representing one of the tone frequencies.

REFERENCES:
patent: 3760269 (1973-09-01), Beeman et al.
patent: 3935395 (1976-01-01), Ball et al.
patent: 3949177 (1976-04-01), Ball et al.
patent: 3959603 (1976-05-01), Nilssen et al.

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