GB1190563A - Improvements in or relating to Electrical Testing Methods and Apparatus. - Google Patents

Abstract

1,190,563. Digital comparators. PLESSEY CO. Ltd. 10 May, 1967 [20 May, 1966], No. 22461/66. Heading G4M. [Also in Division G1] A system for comparing test and reference BCD signals representing values which may have several decades, for use in an amplifier testing arrangement (see Division G1), incorporates a system of exclusive OR gate comparators 91, 10, 11, 12, one for each decade of the BCD signals, to each of which corresponding input and reference BCD digits are applied. Each comparator has an equal signal output 17 and high and low outputs which are connected through inhibit gates via lines 15, 16 to final high and final low OR gates 21, 22, respectively. If a high or low indication is obtained from any comparator, this is applied to the inhibit gates in the output lines of opposite type of all decade stages of lower significance. If a final high or low signal is obtained from the final OR gates, an OR gate passing the equal signals on lines 17 from the comparators is inhibited. The individual decade comparators operate similarly (Fig. 3, not shown), each including four exclusive OR comparators to which corresponding BCD digits from the test and reference signals are applied, and high or low indications on output lines from the comparators being used to inhibit opposite output indications from stages of lower significance.