The DUAL-422 two port interface board is very easy to install as it plugs directly into a slot on the IBM PC/XT/AT and compatibles. The external serial buses are accessed simply through two 9-pin D connectors. In addition to standard data connections, communication standard Request to Send (RTS) and Clear to Send (CTS) control signals also can be used if desired.

Both ports on the DUAL-422 operate independently and each has its own base address and interrupt selection controls. The base address is set by a 7 position DIP switch. It is possible to place the base address anywhere in the computer's I/O address space. In most cases the ports will be set as COM 1 and COM 2. Interrupt level selection for each port is accomplished through separate six position jumpers.

The DUAL-422 is based on the INS16450 UART (compatible with the standard 8250) and allows variable communication parameters to be selected. The serial interface characteristics are fully programmable including 5, 6, 7 or 8 bit character lengths and parity checks: even, odd or none.

Communication at speeds up to 57.6 kbaud over a distance up to 4000 feet is possible with the DUAL-422. (Standard PC baud limitation of 9600 is easily overridden in most cases.) Baud rate can be selected in a wide range of values starting at 120 baud up to 57.6 kbaud.