Voice versus pulsed tone signal discrimination circuit

Details Voice versus pulsed tone signal discrimination circuit Voice versus pulsed tone signal discrimination circuit

1975-11-25

1977-05-31

Claffy, Kathleen H.

179 1SC, 328109, 179 84VF, H04M 322

Patent

active

040271021

ABSTRACT:
Two circuit embodiments are disclosed for discriminating between a voice signal and other audio standard (busy and dial tone) signals on a telephone line. One embodiment measures the frequency of the envelope of the audio signal and decides voice (speech) presence if (glottal) frequencies above 50 hz. are present. The second embodiment measures the cyclic frequency of the audio signal and decides voice (speech) presence if frequencies above 600 hz are present, assuming busy or dial tones are 400 hz. Features of the second embodiment include gating of the timer-counter to prevent the cycle-counter from erroneously counting chatter during rise-time and fall-time of an audio signal.

REFERENCES:
patent: 3725602 (1973-04-01), Hoffman
patent: 3767860 (1973-10-01), Brown
patent: 3927260 (1975-12-01), Amundson et al.
patent: 3949177 (1976-04-01), Ball et al.
Nassimbene, "Speech Analyzing Circuitry," IBM Tech. Disclosure Bull., vol. 6, No. 7, Dec., 1963.
Comer, Kawahara, "Speech Recognition Voicing Det.," IBM Disclosure Bull., vol. 16, No. 10, Mar., 1964.

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