10_DIGIT_CODED_SWITCH

Published:2009/7/14 22:03:00 Author:Jessie | From:SeekIC

Uses seven Texas Instruments positive-logic chips，NAND gates 1-4 and 5-8 are from two SN7400N packages, Two SN7404N packages each provide six of inverting opamps shown Desired coda is set up as combination of 0s and 1s byρresetting ten 2-position switches. To open lock, switches at input for 0 and 1 must be pushed in Sequence of code Arrangement gives 1024 possible combinations but provides much greater protection unless intruder knows that 10 digits are required. Article describes operation of circuit. One requirement of the 2N7496N shift registers is that information be present at serial input before clocking pulse occurs.-K. E. Potter, Ten-Digit Code-Operated Switch or combination Lock, Wireless World, May 1974, P 123.



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