Cromemco - PRI Board 
The Cromemco PRI parallel printer interface board was designed to permit the simultaneous operation of the Cromemco 3703 or 3779 dot matrix printer and the 3355A fully formed character printer.

Features included automatic ribbon control for the fully formed character printer, and supports interrupts. On these old printers the ribbon had to be raised and lowered for proper character printing. The PRI board had a timer circuit so the ribbon was in place before the character was printed. It would stay raised until no more characters came within a 1 second timeout. Although the I/O ports were factory set they could be easily changed by the user.
 
The manual for this board can be obtained here.