Electronic lock electronic project using LS7220 integrated circuit

Using electronic diagram below can be made a very simple electronic lock that uses few electronic components .
Electronic lock from this circuit diagram is built using LS7220 integrated circuit.
The keyboard has 10 keys for numbers 0 ... 9, four of them used to fix the code, which are connected to pins 3 ... 6 of the integrated circuit. Unused keys are connected to the reset input. pin 2. Circuit diagram shows the connections for the code number 4179 (pins 3 ... 6 cause code sequence: sampling circuit 3 is connected to the key pin 4, pin 4 to 1 key etc.). When you type the correct code. Output pin 13 of integrated circuit connected to the positive supply voltage and 12 T1. Therefore, these transistors conduct, and acting door opener. Resistance R2 and capacitor C3 determine how long the door remains active opener. If the door is open at this time, the code must retype. If necessary. this time can be increased by choosing a higher value for C3.
Supply voltage for the circuit and the door opener can be obtained from a transformer 8 V.

Circuit Diagram: