Method and apparatus for detection of fax calls

Details Method and apparatus for detection of fax calls Method and apparatus for detection of fax calls

1999-02-10

2000-06-13

Chan, Wing F.

Telephonic communications

Telephone line or system combined with diverse electrical...

To produce visual-graphic copy

379 9309, 37910015, 358442, H04M 1100

Patent

active

060758473

ABSTRACT:
A method and system for detecting fax calls in a network that alternatively operates in either a voice mode or a fax mode. A detection threshold is first initialized, a first detector detects whether a calling tone has been transmitted from a calling fax machine to a called fax machine, and a second detector detects whether an identification tone has been sent from the called fax machine to the calling fax machine. If the calling tone has been transmitted from the calling fax machine to the called fax machine the detection threshold is decremented a first amount, if the identification tone has been transmitted from the called fax machine to the calling fax machine the detection threshold is decremented a second amount, and if both the calling tone and the identification tone have been sent the detection threshold is decremented a third amount. A flag measure is generated by monitoring, with a third detector, signals sent from the called fax machine. The flag measure is representative of the number of information flags detected by the third detector. The flag measure is compared to the detection threshold and, if the flag measure exceeds the detection threshold, a fax call is detected. The detection of the fax call may then be used to switch a network from voice mode to fax mode. The vocoder used in the voice mode is temporarily muted when the detection threshold is first exceeded in order to confirm the existence of the fax call before switching from voice mode to fax mode.

REFERENCES:
patent: 5117453 (1992-05-01), Plasecki et al.
patent: 5892816 (1999-04-01), Shih et al.

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