Here are many ways to you will provide the protection you deserve. 4 Alarm Control Systems has been providing Fire and Security The Simple 4 Digit Alarm Control keypad Circuit Diagram must be the kind with a common terminal and a separate connection for each key. On a 12-key pad, look for 13terminals. The matrix type with 7 terminals will NOT do. The Alarm is set by pressing a single key. Choose the key you want to use and wire it to `E`. Choose the four keys you want to use to switch the alarm off, and connect them to `A B C & D`. Your code can include the non-numeric symbols. With a 12-keypad, over 10 000 different codes are available. Wire the comm onto R1 and all the remaining keys to `F`. When `E` is pressed,current through D2 and R9 switches Q5 on. 4 digit Alarm Control keypad Circuit Diagram The relay energies, and then holds itself on by providing base current for Q5 throughR10. The 12-volt output is switched from the “off ” to the “set ”terminal, and the LED lights...