COM-422 from $199
RS-232/422 Interface Board For IBM PC/XT/AT Compatibles

The COM-422 I/O plug in expansion board is designed to interface to the RS-422, RS-232 or current loop serial interface bus through a 25 pin or 9 pin connector. The RS-232 interface includes all standard bus control protocols such as data set ready, clear to send and data terminal ready. If desired, these communication control signals can be disabled. The RS-422 interface can use standard "clear to send" and "request to send" control lines or can be set to only send and receive data. All selections of RS-232 or RS-422 and protocol desired are made with switches on the board. For long distance transmission, the COM-422 is able to communicate up to 56 kilobaud at distances up to 1.2 kilometers. Data transfer rate is software selectable.