DTMF signal judging apparatus

Details DTMF signal judging apparatus DTMF signal judging apparatus

1995-02-03

1996-12-24

Zele, Krista M.

Telephonic communications

Centralized switching system

Switching controlled in response to called station...

379386, H04M 1515

Patent

active

055880525

ABSTRACT:
A DTMF signal judging apparatus includes a first power calculator, and second power calculator and a judging apparatus. The first power calculator calculates the overall power of an input signal or the power of the input signal outside the DTMF frequency band. The second power calculator calculates the power in the DTMF frequency band; or more specifically, calculates the power in both the higher and lower frequency band portions of the DTMF frequency band. The judging apparatus then compares the output from the first and second calculators, and determines whether the input signal is a DTMF signal based on the comparison.

REFERENCES:
patent: 4042790 (1977-08-01), Richards
patent: 4091243 (1978-05-01), Mizrahi
patent: 4191862 (1980-03-01), Hughes
patent: 4922528 (1990-05-01), Hubert
patent: 5117369 (1992-05-01), Yoshikawa
patent: 5119322 (1992-06-01), Stroobach
patent: 5214693 (1993-05-01), Chujo

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