Apparatus for multifrequency signalling tone detection

Details Apparatus for multifrequency signalling tone detection Apparatus for multifrequency signalling tone detection

1985-02-28

1986-07-08

Dwyer, James L.

Communications: electrical

Land vehicle alarms or indicators

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

34082571, H04M 100

Patent

active

045994951

ABSTRACT:
Apparatus for detection of the presence of signalling tones in telephony is provided wherein the output levels for four band-pass filters in the VF band are processed by means of logic circuits to yield a "tone present" decision. Selection of two critical thresholds permits the apparatus to operate optimally within its environment of trading off talk-off immunity with minimum acceptable signal-to-noise ratio.

REFERENCES:
patent: 3912869 (1975-10-01), Ullakko
patent: 3937899 (1976-02-01), Denenberg
patent: 4107475 (1978-08-01), Carlquist et al.

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