Circuits embodying electronic counters

850,583. Comparing digital data. SOLARTRON ELECTRONIC GROUP Ltd. March 17, 1958 [March 25, 1957], No. 9771/57. Class 106(1). Apparatus adapted to be fed with successive groups of pulses and to determine the maximum or minimum number of pulses in a group, comprises two electronic counters and a computor which, after each group of pulses is received, causes that counter storing the higher or lower count to be reset and thereafter activated to count the pulses in the next group. The arrangement shown forms part of a character-reading apparatus as described in Specification 850,581. During each line of a scan, one of the counters 60, 61, determined by the state of bi-stable device 64, counts the pulses received from clock generator 18 until a black element is sensed which triggers bi-stable device 63 to inhibit the counter input gates 65, 67. The voltages on lines 73, 74, which correspond to the values registered on the counters, are then compared in circuit 62 which primes gate 66 or 69 according to whether the higher count is registered in counter 60 or 61. Suppose e.g. that counter 61 has counted the last group of pulses. If this counter registers the higher count, the comparator 62 and device 64 activate gate 69 and thus inhibit associated gate 76; an interline pulse received from circuit 45 then passes through delay network 79 and gate 70, opened by device 64, thus resetting counter 61. If, however, counter 61 registers the lower count, neither of the gates 66, 69 is activated and neither of gates 75, 76 is inhibited; the interline pulse is therefore passed to both inputs of device 64 which is then switched over, thus opening gate 67 to cause counter 60 to be reset by the delayed pulse from 79. When the scanning process is completed, one of the counter outputs A, B will represent the smallest number of blank elements counted (the other counter registering zero), and will thus indicate the number of blank elements separating the most " northerly " point on the character being scanned from the north of the scanning raster. A slightly modified arrangement (Fig. 2, not shown) similarly obtains an indication of the most southerly point. The apparatus of the invention may be employed also for determining the maximum or minimum values of a graph obtained, e.g. from a spectrometer, and scanned photo-electrically, or for determining the maximum or minimum amplitude of pulses. The counter outputs may be recorded, e.g. on magnetic tape or by a printer.