“Inside the WOPR is an Espduino with a prototyping shield on top of it. You also need a buzzer and a relay, a transistor (universal NPN type), a 1k5 resistor and a 1N4148 diode. You can get all those parts at your favorite Arduino webshop. The buzzer is used to signal when a hacker tries to operate your switch. Don’t worry: the switch has some security build in. Note on the wiring of the relay: I wired it so that the NO contact (normally open) of the relay switches the device. That way the device will be on after a power failure (even during a power failure).”