Knowledge of diodes, relays, and resistors is essential to being a proficient alarm installer. For example, with just relays and a few diodes, you can build a circuit to work with your existing alarm or keyless entry to start your vehicle. Add a capacitor and a resistor to a relay and a diode and you've created a timer to use with it. Once you master these, you'll think of all kinds of things to create and add to your system as well as your customers'.