This 'Combination Terminal' can be used for more than just locking, but it's more effective for that.
this idea was spawned off of trying to build an AI out of observers, using command blocks to activate functions that it could detect and act accordingly. (IE Farming [using a piston attachment and command to harvest and plant a seed] to make an infinite food source that you would only have to collect from time to time.)
the combination is slightly harder to crack due to its ability to reset the circuit if the wrong buttons are pressed, making it good for keeping your diamonds and other things safe. the entry port could be made using pistons but it has no cool-down for when the pistons retract so get in, do whatever you need to, then get out and lock the system by retracting the signal extenders AFTER you shut off off the lock power
this lock doesn't use the standard redstone lock system, instead it uses multiple layers of pistons as a way to extend the signal, and can be made to where you need to activate specific ones in order to open it.
(We already have this version of a lock used in my laboratory on our guilds server. It powers a 3x3 piston door)

See you in the workshop, Pilots!
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