Light circuit diagram: Intelligent Electronic Lock

This intelligent electronic lock circuit is built using transistors only. To open this electronic lock, one has to press tactile switches S1 through S4 sequentially. For deception you may annotate these switches with different numbers on the control panel/keypad. For example, if you want to use ten switches on the keypad marked 0` through 9`, use
Light circuit diagram: Intelligent Electronic Lock - schematic

any four arbitrary numbers out of these for switches S1 through S4, and the remaining six numbers may be annotated on the leftover six switches, which may be wired in parallel to disable switch S6 (shown in the figure). When four password digits in 0` through 9` are mixed with the remaining six digits connected across disable switch terminals, energisation of relay RL1 by unauthorised person is prevented. For authorised persons, a 4-digit password number is easy to remember. To energise relay RL1, one has to press switches S1 through S4 sequentially within six seconds, making sure that each of the switch is kept depressed for a duration of 0. 75 second to 1. 25 seconds. The relay will not operate if on` time duration of each tactile switch (S1 through S4) is less than 0. 75 second or more than 1. 25 seconds. This would amount to rejection of the code. A special feature of this circuit is that pressing of any switch wired across disable switch (S6) will lead to disabling of the whole electronic lock circuit for about one minute. Even if one enters the correct 4-digit password number within one minute after a disable` operation, relay RL1 won`t get energised. So if any unauthorised person keeps trying different permutations of numbers in quick successions for energisation of relay RL1, he is not likely to succeed. To that extent, this electronic lock circuit is fool-proof. This electronic lock circuit comprises disabling,...

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