Redundancy reduction system for facsimile transceivers

Details Redundancy reduction system for facsimile transceivers Redundancy reduction system for facsimile transceivers

1976-06-16

1978-06-13

Britton, Howard W.

Facsimile and static presentation processing

Facsimile

Recording apparatus

358260, H04N 334

Patent

active

040952487

ABSTRACT:
A facsimile transmitter-receiver system which is adapted for use over a limited band width transmission path employs a redundancy reduction unit to speed-up transmission time by rapidly sweeping the transmitters single scanning beam in full or partial search passes across proposed data free areas of a source document. In the horizontal direction a transition to partial fast search during a horizontal pass is made beyond a proposed right hand data boundary and is accompanied by a one line space temporary downward deflection or bias of the scanning beam, which facilitates search for new data boundaries and also permits the system to make a slow scan retrace of a line (by eliminating the bias whenever data is actually found in the search pass). Fast search in the vertical direction is effected by two related methods: (1) The use of a wide search pass in which the scanning beam is effectively widened during a horizontal pass, preferably by zigzagging the beam up and down with a simple vertical modulation which is many lines wide and; (2) By thereafter sufficiently increasing the spacings between successive wide search passes of the scanning beam so that each successive wide search pass is only slightly overlapped with the bottom of the preceding wide search pass. Major data free areas in the horizontal direction are therefore scanned at a much higher velocity than are data filled areas; and major data free areas in a vertical direction are scanned with many fewer passes of the wide search scanning beam. A major speed-up in transmission speed and consequent reduction in time and cost of transmission is thereby obtained.

REFERENCES:
patent: 3366734 (1968-01-01), Jurk
patent: 3502803 (1970-03-01), Bigenwald
patent: 3643016 (1972-02-01), Dattilo
patent: 3646256 (1972-02-01), Jacob
patent: 3730988 (1973-05-01), Shimizu
patent: 3955045 (1976-05-01), Ford

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