The Redarc Voltage Sensors are used to monitor the 12V or 24V supply in a negative earth automotive system. Depending on the voltage, the internal relay switches its common contact to either the normally closed contact or the normally open contact. These contacts are connected to the WHITE, GREEN and BLUE wires respectively. When the voltage rises above the set point, the 10A internal relay is energized. This disconnects the WHITE wire from the GREEN wire and connects it to the BLUE wire. When the voltage falls below the set point the internal relay is de-energised. This disconnects the WHITE wire from the BLUE wire and connects it to the GREEN wire.