It needs rectifier diodes so it doesn't interfere with the turn signals, since diodes let electricity trough one way and not in reverse.. And prevents the turn signals interfere with the hazard lights. The red wire from the ignition comes straight from the battery, the black wire from the ignition goes to power the rest of the system. So this system works with or without the ignition on. So the BLINKER relay can be used as turn signals and also to power hazard lights.