Hệ thống khóa mạch điện tử dùng CD4013

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This
circuit is very basic to build. To open a the lock which is connected
to the K1 Load you must press each momentary switch in the correct
sequence. The sequence used in this circuit is S1,S2,S3,S4. If any of
the other switches are pressed the circuit will reset and you will need
to start over. Depending on how you wire the switches, you can use any
4 switch combination.