The SRC-4 interfaces four optically isolated inputs and four SPDT relays to a RS-232 port. The SRC-4 can notify a users PC software program that any of four optically isolated inputs have been opened or closed and allows the users software to control four SPDT relays. Communication with the SRC-4 is accomplished via short "burst" type ASCII commands from the users PC. In addition to the standard ASCII control command mode, the SRC-4 ‘s inputs can be configured to generate custom ASCII serial strings up to 14 characters long. Similarly the SRC-4’s relays can be configured to respond to custom ASCII serial strings up to 14 characters long for on/off or pulse control. Two units may be operated in a standalone mode (master/slave mode) to form a "Relay extension cord," with four channels of control in each direction. By default the unit operates at 9600 baud, but baud rates from 2400 to 115k may selected using the automatic baud rate detection feature. Wiring is simplified with removable euro-block screw terminals. The SRC-4 is powered by a surge protected internal power supply and supplied with a universal 9 volt DC switching power adapter. An optional USB-RS-232 smart cable adapter is available. Up to four SRC-4’s may be rack mounted on the optional RA-1, 1-RU mounting shelf. Ethernet capabilities are available with the I/O Sentinel® 4.