The USB-RLY16 provides eight volt free contact relay outputs with a current rating of up to 16Amp each. The processor is powered and instructed from any standard USB bus and the relay power is obtained by the DC power input adaptor. The DC input jack is 2.1mm with positive core polarity, DC supplies are required to supply at least 500mA at 12vdc. The relays are SPCO (Single Pole Change Over) types. The normally open, normally closed and common pins are all available on the screw terminals.