Tone detection

Details Tone detection Tone detection

1997-09-11

1999-12-21

Eisenzopf, Reinhard J.

Telecommunications

Having single-channel telephone carrier

Including call signaling

379386, H04B 100

Patent

active

060060832

ABSTRACT:
AMPS (Advanced Mobile Phone System) ST (signalling tone) is detected by a tone detector in which samples of a demodulated signal are amplitude limited to remove click energy, and the limited signal is bandpass filtered, using a notch filter and summer, to limit it to the range of possible ST frequency. Power of the bandpass filtered signal is detected, and compared with detected power of a version of the bandpass filtered signal from which any sinusoidal signal has been eliminated, independent of frequency, to provide for ST detection. A function [x(k)+x(k-2)]x(k-2)-[x(k-1)+x(k-3)]x(k-3) for successive samples x(k) of the bandpass filtered signal is used for the sinusoidal signal elimination. The invention can also be used to detect other tones.

REFERENCES:
patent: 4450417 (1984-05-01), Folkmann
patent: 4546490 (1985-10-01), Miller-Thomson et al.
patent: 4599495 (1986-07-01), Richards
patent: 5408529 (1995-04-01), Greaves
patent: 5818929 (1998-10-01), Yaguchi

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