This is a "standard" 4 channel relayboard that should be powered with 5V or 12V depending on what variant you choose. The input pins should be pulled low to activate the relay Features: Low cost way to control larger voltages and currents. Supplied assembled On-board switching transistors. On-board back EMF protections. On-board LED-indicator for power On-board LED-indicators for each channel 10 amp 250v rated relay. The board is not tested to be used with mains voltages!