Keyboard actuated electronic lock - has link re-programmable codes and uses links to set required access code to provide number of attempts counter and time limit

摘要

The electronic lock uses a four by four keyboard whose outputs are converted to Binary Coded Decimal numbers by an integrated circuit encoder. The encoded outputs are latched and passed through programming links. The links allow simple alteration of the entry code to multiple input NAND gates. If an incorrect sequence is entered the gates are inhibited and a count of the number of incorrect sequences initiated. Monostable circuits provide an allowed time for entry. If the entry code is not entered within the allowed number of attempts and within the set time the lock becomes inoperative for a period. If the correct code is entered the multiple input NAND gates drive a transistor which, through a relay, operates the electric latch.