In Reply to: How about a crash course on diodes? (eom) posted by Zeroster on June 07, 1999 at 18:08:52:
Diodes are semiconductor devices that, in the case of rectifier diodes, which are the ones you are interested in, will only allow current to flow in one direction( towards the cathode). So, when you want to prevent current from one wire running backwards into another wire that you connected to it( for example, the trunk and hood trigger wires), you put a diode on each wire before you connect them. You must put them in the correct orientation or they will restrict current flow in the direction you want and allow it in the wrong direction. They are rated as to how much voltage that can take before they backflow and lose their directional function. Other types of diodes are LEDs or light emitting diodes. These are the type that provide the little lights all over your dashboard. The diodes look just like resistors. Two wires with a tiny ceramic cylinder in between.