GB1370342A - Facsimile apparatus - Google Patents

Abstract

1370342 Copying by scanning MATSUSHITA ELECTRIC INDUSTRIAL CO Ltd 14 Sept 1971 [16 Sept 1970] 42858/71 Heading H4F A facsimile transmitter, Fig. 2, codes the run lengths of successive black and white marks on a scanned document 10 into digital form at 3, only one, or at most nine, marks being coded during each line scan. The fibre optics scanning tube 7 continuously scans one line of document 10, and the output from a phot-ocell 11 is fed to a control circuit 2. One (or more) mark signal is read by circuit 2 and passed to encoder 3 and while this mark is being encoded the tube 7 continues to line scan but circuit 2 does not read the resulting output. As the penultimate coded bit is fed through a register 6 a signal is generated to cause the circuit 2 to read the next mark (or group of marks). When all the marks related to one line have been encoded a signal causes sub-scanning control circuit 4 to advance the document 10. The correct mark (or group of marks) to be read is selected by use of a coincidence circuit (28, Fig. 6, not shown) and two binary counters, one (25) counting pulses related to the length of a specific line already read, and the other (26) counting pulses from the beginning of the required line scan of tube 7, circuit 4 being operated by overflow of the first counter (25), the equivalent receiver (Fig. 10, not shown) using similar counters and coincidence circuit as well as receiving the stepping pulses which are amplitude modulated on to a carrier, the coded marks being transmitted on a carrier at a different frequency. The coding of the pulses is such that mark run lengths of 1 and 2 (as measured by clocking pulses) are coded as 10 and 11 respectively whereas a number n # 3 is coded by taking the binary number of n-1. This binary number has m digits and m - 1 zeros are added in front of the binary number n-1, e.g. if n = 3, n-1 = 2, binary n-1 = 10 so m = 2, m-1 = 1, and coded number = 010. The resulting signal is decoded by counting zeros to determine the divisions between coded marks as shown in Fig. 9.