This relay board contains 12 independent 3A 30VDC, 3A 250VAC relays. Each of them can be controlled via serial command. (A=1) (B=1) (C=1) (D=1) ... (H=1) to turn on the corresponding relay or (A=0) (B=0) (C=0) (D=0)...(H=0) to turn off the  corresponding relay. (A=?) for example will return the state of the relay A. The return is either (A=1) for the On state of (A=0) for Off state.

Power input: 9V to 24V center positive

Interface: DB9 female (Baud rate: 9600, 8-N-1, No flow control)