Powered and Controlled from the USB bus.
The relays used on this board are premium ultra low power 50mW coil types. 

Relays - 2
Analogue/digital inputs - 8 (5V max, choice of 5V, 4.096V or 2.048V scale for Analogue conversion)
Power - Powered from standard USB bus 
Control interface - USB 
Relay current - Up to 1Amp @30vdc or 60vac. 500mA@110vac. 250mA@250vac 
Connections - Screw Terminals for N/O N/C and Common contacts.

Resources:

Datasheet and manual