GB1471420A - Signal interleaving system for binary pulse signals - Google Patents

Abstract

1471420 Data transmission; multiplexing KOKUSAI DENSHIN DENWA KK 10 April 1974 [12 April 1973] 15869/74 Heading H4P An arrangement, particularly for facsimile transmission wherein other information may be transmitted when bits in blocks all have the same value, comprises a first store and signal change detecting device which provides an inverted signal on presence of change in present and previous blocks, whereby the present block is sent if change is detected together with a flag bit(s), but other information is sent, with different flag bit(s) if nil change(s) are detected. At a receiver, the flag bit(s) determine destination of incoming information. An analogue or digital signal on terminal 101 is sampled at 2, the result being passed to a 4-stage shift register 4 which when full is examined, together with the last bit in a shift register 7 by a bit change detector 5. Provided at least one bit differs from the remainder, flip-flop 11 is set to 1 and gate 6 transfers content of 4 to 7 and thence to 8 for transmission with a flag bit 0. With no change, flip-flop 11 is set or remains at 0 and other information from memory 10 is passed through 8 and transmitted together with a flag bit 1. If there are a plurality of sources of other information, an appropriate number of flag bits will be transmitted. At the receiver a flag bit detector (308) Fig. 2 (not shown) energizes an appropriate gate, e.g. (204, 206) to divert incoming blocks appropriately. A shift register receiving the main transmission has a control circuit to insert untransmitted facsimile &c. bits. The arrangement permits additional transmitted information during periods which would otherwise be occupied by redundant bits.