Features:
Has an option to change the ID (from ID 01 to ID 7) manually through a DIP Switch placed near UART connector.

 
Model:
URT8CRD

UART port levels:
5V

Dimensions:
KMTronic_8Relay_Dimension.pdf

Required power:
12VDC / minimum 600 mA.

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

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

Commands:
Relay commands:
OFF command : FF xx 00 (HEX) or 255 xx 0 (DEC)
ON command : FF xx 01 (HEX) or 255 xx 1 (DEC)

FF 01 00 - First relay OFF command
FF 01 01 - First relay ON command

FF 02 00 - Second relay OFF command
FF 02 01 - Second relay ON command

.......
 
FF 08 00 - Eight relay OFF command
FF 08 01 - Eight relay ON command

Software examples:
https://info.kmtronic.com/uart-relays.html