Parameter: Supply voltage: DC 5V 12V 24V ( 5 - 24V). Communication chip: MAX232. Communication protocol, format: Serial port 232 communication, the protocol is very simple, use the serial port debugging software to send the character type "A" relay to open, send the character type "a" relay to close. Communication format: (9600, 8, NONE, 1). Baud rate: 9600, 8 bits, no parity, 1 stop bit Package Included: 1Pcs 12V USB Control Switch Relay Module