Method and apparatus for fast DTMF detection

Details Method and apparatus for fast DTMF detection Method and apparatus for fast DTMF detection

2008-05-06

2008-05-06

Singh, Ramnandan (Department: 2614)

Multiplex communications

Pathfinding or routing

Combined circuit switching and packet switching

Reexamination Certificate

active

10688642

ABSTRACT:
A fast DTMF detector for filtering a packetized linear voice signal to identify whether the voice signal contains a DTMF tone. The detector includes a plurality of parallel notch filters for knocking down DTMF tones. The energies of the filtered signals output by the notch filters are calculated and criteria based upon the calculated energies are applied to determine if the voice signal contains a DTMF tone. The criteria include an energy differential test, a twist test, a low frequency tolerance test, a high frequency tolerance test, a packetized linear voice signal energy level test, a dial tone filtered signal energy level test, and a 1004 Hz filtered signal energy level test.

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