Facsimile and static presentation processing – Facsimile – Auxiliary signal
Reexamination Certificate
1997-12-12
2001-12-04
Williams, Kimberly A. (Department: 2622)
Facsimile and static presentation processing
Facsimile
Auxiliary signal
C358S442000, C358S468000, C375S222000
Reexamination Certificate
active
06327053
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a system and method for suppressing multiple modulation and demodulation of a facsimile signal in a telecommunications network.
BACKGROUND OF THE INVENTION
In a telecommunications network, digital private branch exchanges (PBXs) are interconnected by pairs of modulator-demodulator (mod-demod) machines for use in transmitting facsimile (fax) signals. The mod-demod machines provide for a savings in bandwidth and thus transmission cost by demodulating a fax signal down to a baseband level before passing it across connections in the network and by subsequently remodulating the signal for transmission to a PBX. In particular, one mod-demod machine of each tandem pair demodulates a 64 k bits per second (bps) pulse code modulation (PCM) signal down to a baseband level for transmission to other mod-demod machines in the network. The other mod-demod machine of the pair remodulates the baseband signal back to a 64 k bps PCM signal for subsequent transmission in the network.
Unfortunately, modulation and demodulation introduce distortion and delay into a signal, and when a signal is subjected to repeated modulation and demodulation cycles, each cycle adds distortion and delay. Repeated modulation and demodulation of a fax signal often results when a connection established within a telecommunications network includes more than one PBX. The increased amount of distortion resulting from repeated modulation and demodulation is undesirable, as it may result in a loss of data or errors in transmitted data.
Accordingly, a need exists for an improved method of transmitting fax signals in a digital communications network.
SUMMARY OF THE INVENTION
A mod-demod machine consistent with the present invention receives a protocol message related to a fax signal and places itself in a mode in response to the protocol message. The mod-demod machine also receives the fax signal and processes the fax signal according to the mode.
A method consistent with the present invention for transmitting a fax signal through a mod-demod machine receives a protocol message related to a fax signal and places the mod-demod machine in a mode in response to the protocol message. The method receives the fax signal and processes the fax signal according to the mode.
An article of manufacture consistent with the present invention for controlling modulation and demodulation of a fax signal transmitted through a network with multiple mod-demod machines includes a computer-readable medium with computer-readable information. The information includes a protocol message for transmitting an associated fax signal, and the protocol message includes a computer-readable mode signal for use by a mod-demod machine in controlling modulation and demodulation of the associated fax signal.
REFERENCES:
patent: 4668994 (1987-05-01), Takahashi et al.
patent: 4924480 (1990-05-01), Gay et al.
patent: 4961185 (1990-10-01), Sawada
patent: 5210826 (1993-05-01), Takeda et al.
patent: 5216519 (1993-06-01), Daggett et al.
patent: 5220560 (1993-06-01), Ogasawara
patent: 5249218 (1993-09-01), Sainton
patent: 5268770 (1993-12-01), Yukino
patent: 5307174 (1994-04-01), Saito
patent: 5418628 (1995-05-01), Perkins
patent: 5461488 (1995-10-01), Witek
patent: 5585938 (1996-12-01), Imamura
patent: 5711012 (1998-01-01), Bottoms et al.
patent: 5742639 (1998-04-01), Fasulo, II et al.
patent: 5751796 (1998-05-01), Scott
patent: 5752199 (1998-05-01), Scott
patent: 5784633 (1998-07-01), Petty
patent: 5878078 (1999-02-01), Griffin et al.
patent: 5966663 (1999-10-01), Gleason
patent: 0 478 205 A2 (1992-04-01), None
patent: 0 494 687 A2 (1992-07-01), None
patent: 0 714 186 A2 (1996-05-01), None
Tomcik et al., “Facsimile Compression Through Demodulation in Packet Networks,”IEEE, pp. 1699-1703 (1992).
European Search Report, dated Mar. 29, 2000.
ITU-T Recommendation T.30: Terminal Equipments and Protocols for Telematic Services: Procedures for Document Facsimile Transmission in the General Switched Telephone Network (Mar. 1993).
Finnegan, Henederson, Farabow, Garrett & Dunner, L.L.P.
Nortel Networks Limited
Williams Kimberly A.
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