USB-RLY02-SN - Módulo 2x16A Relés USB

Powered and Controlled from the USB bus.

Relays - 2 with integrated snubbing of the normally open terminals
Power - Powered from standard USB bus 
Control interface - USB with a mini B connector
Relay current - Up to 16Amp @24vdc or 250vac 
Connections - Screw Terminals for N/O N/C and Common contacts.

Snubbers
Optional integrated snubbers have be added to the module between the common and normally open poles. When inductive loads are to be used the optional snubbers suppress the switching spikes and relay arc associated with such loads.
We have a simple guide here

Full USB-RLY02-SN Documentation

Examples:
Linux
Linux GCC - A command line tool that will set the relay states according to input from the user
Linux with Mono and Xbuild (C#) - Simple example of switching the relays

Mac
Xcode - Simple example of switching the relays

Microsoft Windows
Visual C# Express - Simple example of switching the relays
Visual Basic Express - Simple example of switching the relays