Dual tone detector operable in the presence of speech or backgro

Details Dual tone detector operable in the presence of speech or backgro Dual tone detector operable in the presence of speech or backgro

1993-06-02

1995-04-18

Dwyer, James L.

Telephonic communications

Supervisory or control line signaling

Signal receiver

379283, 327 46, H04M 150

Patent

active

054085292

ABSTRACT:
A dual tone detector (100) for a single dual tone, a dual tone multi-frequency (DTMF), or similar system processes an input signal through both bandpass (103) and band reject (104) tone detectors. If both the bandpass (103) and band reject (104) tone detectors detect a tone, then the dual tone detector (100) provides a tone detect output signal. If only the bandpass tone detector (103), which is susceptible to false tones, detects a tone, then a voice input signal is muted and the tone detector (100) activates the tone detect output signal only if both the bandpass (103) and band reject (104) tone detectors subsequently detect a tone. In one embodiment, a dual bandpass/band reject tone detector (120) processes the input signal through shared front-end band reject filters (121, 122), limiters (124), resonators (127, 128), and a processing section (130) in order to save circuit area. Limiter and peak detector functions are also implemented in shared circuitry to further reduce circuit area.

REFERENCES:
patent: 4347408 (1982-08-01), Ito et al.
patent: 4626629 (1986-12-01), Premoli et al.
patent: 5214693 (1993-05-01), Chujo
Clark, et al.; "Station Signaling and Announcement Sybsystem: Hardware for Automated Coin Toll Service"; The Bell System Tech. Jour.; vol. 58, No. 6, pp. 1225-1249 (1979).
"Dual Tone Multiple Frequency Receiver"; Motorola Telecommunications Device Data; pp. 2-540-2-544 (1989).

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