Time compression receiver

Details Time compression receiver Time compression receiver

1974-09-04

1976-01-06

Claffy, Kathleen H.

H04M 150

Patent

active

039314804

ABSTRACT:
Time compression receiver for detecting the signalling tones in a DTMF (dual tone multi-frequency) format present on eight receiver input lines. A multiplexer repeatedly samples the input signals present on the eight input lines. These analog samples are converted to digital samples and stored in a memory. Stored samples are read out for each input line in order while new samples are being written into the memory. Samples are read out at twice the rate they are written in. The samples are converted to analog signals and passed through a low pass filter. The frequencies present in the resulting signal are speeded up by a factor of sixteen over the frequencies of the signalling tones present in the input signal from which it was derived. The signal frequencies are passed through reject filters, comparator and limiter circuits, a bank of tone filters, and level detectors to check for each possible resulting frequency and to produce an indication of the presence or absence of each.

REFERENCES:
patent: 3445606 (1969-05-01), Brightman
patent: 3578919 (1971-05-01), O'Neill
patent: 3773981 (1973-11-01), Stilwell
patent: 3794763 (1974-02-01), Bolidweijns

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