Whenever two bare wires have contact with water, the light emitting diode will light up. The device is suitable to release alarm in case of overflowing rain barrels and gutters. Operating voltage: 9 V/DC. Accessories available : kit B197 - Relay card 12 V/DC, which could be connected with this kit and could switch through the relay contact other devices (e.g. pumps) up to current consumption of 3 A