This simple circuit is a NOR gate simulated with LEDs and whose inputs are made using keys. To supply the 12V circuit, use a 1k-ohm resistor. The LED can be of any color and more inputs can be connected, that is, more switches in parallel.

This simple circuit is a NOR gate simulated with LEDs and whose inputs are made using keys. To supply the 12V circuit, use a 1k-ohm resistor. The LED can be of any color and more inputs can be connected, that is, more switches in parallel.