Telephonic communications – Call signal generating
Patent
1994-12-13
1998-10-06
Matar, Ahmad F.
Telephonic communications
Call signal generating
379283, 379351, 379386, H04M 150
Patent
active
058189297
ABSTRACT:
The total energy of a signal that has entered from a telephone line is detected before the signal is applied to an AGC circuit. After the signal is applied to the AGC circuit, the energy of a DTMF signal, which comprises one frequency from four high group frequencies and one frequency from four low group frequencies, is detected through a band-elimination filter having a short energy-propagation delay time with respect to pass-band frequencies. By detecting the DTMF signal based upon the detected energies, detection of the DTMF signal can be performed in a short period of time and erroneous detection can be suppressed.
REFERENCES:
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patent: 5119322 (1992-06-01), Stroobach
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patent: 5392348 (1995-02-01), Park et al.
patent: 5408529 (1995-04-01), Greaves
Canon Kabushiki Kaisha
Matar Ahmad F.
Saint-Surin Jacques M.
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