The complete includes:
- One UART output controller (12V)

Required power:
12VDC /  minimum 1000 mA.

UART port levels:
5V

Standby current:
(Relays OFF) - 21 mA
One Relay ON - 57 mA
Two Relays ON - 91mA
All Relays ON - 300 mA

Features:
- Each relay has an LED to indicate when it is operated.
- Relay outputs can be used to turn ON/OFF lights, motors and other devices.

Specifications:
Relays have Normally Open (NO) and Normally Closed (NC) Contacts each capable of switching max:
- 12VDC/15A
- 24VDC/15A
- 125VAC/15A
- 250VAC/10A

Dimensions:
http://info.kmtronic.com/KMtronic-8Relay-Dimension.pdf

Communication Parameters:
8 Data, 1 Stop, No Parity
Baud rate : 9600

Commands:
FIRST channel commands:
OFF command : FF 01 00 (HEX) or 255 1 0 (DEC)
ON command : FF 01 01 (HEX) or 255 1 1 (DEC)
...
...
...

EIGHT channel commands:
OFF command : FF 08 00 (HEX) or 255 8 0 (DEC)
ON command : FF 08 01 (HEX) or 255 8 1 (DEC)

Software examples:
http://www.info.kmtronic.com/usb-rs232-rs485-relays.html