GB1476476A - Facsimile system - Google Patents

Abstract

1476476 Data transmission; facsimile systems PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 29 May 1974 [1 June 1973] 23767/74 Heading H4P In a facsimile system, black/white picture elements as represented by binary values are compared in groups from at least two adjacent lines and for transmission are coded to produce for a group of all one binary level a first fixed coded signal (e.g. a 1) but when at least one level is different a second fixed coded signal (e.g. a 0) together with further binary signals representative of individual elements of the group. In one embodiment 6 picture elements from m = 3 lines and n = 2 columns form a group. A 3 line scanner 11 output is passed into flip-flops 21-23 which are gated through NAND's 24-26 into D flip-flops 27-29. Components 21-29 act as a parallel/serial converter, output being taken from flip-flop 27 (for n = 3 a further group of flip-flops will be needed) to NAND's 30, 32 to a memory 4 also receiving information through NAND's 31, 33. Scanner inputs are also applied through NAND 36 forming a comparator which if an all white group is detected gives a 0 hence flipflops 37, 38 also give 0 and hence through gates 30-33, 35 a clocking 1 pulse is provided on A20 which allows a 1 pulse on A19 into store 4. However if any black information is present in a group the circuit is reset and a series of clocking 1 pulses is presented on A20 which provides an initial 0 followed by six 0's and/or l's representative of the individual picture elements given on A19 for storing at and subsequent transmission to a receiver. At the receiver line start and end signals are derived from a store 10 in a manner not disclosed which are applied together with decoded signals to a display device 40. In an alternative arrangement (Fig. 6, not shown) a single line scanner (11-) is employed signals from which are clocked directly into a flip-flop (23) through one line delay into (22) and two line delay (21).