http://www.info.kmtronic.com/software/Raspberry_PI/Raspberry_PI_KMTronic_USB_Relay.zip
USB One Relay commands:
FF 01 00 - OFF command
FF 01 01 - ON command
FF 01 03 - Status request command
> FF 01 xx - Reply from relay
where xx is status: 01 - Relay is ON, 00 - Relay is OFF
Set baudrate to 9600b/s
Switch ON relay
Switch OFF relay
Status request