PURPOSE: To communicate with various kinds of external devices through the unified shape interface board by providing an option adapter to convert a non- unified shape connector into a unified shape connector in addition to a data buffer and a protocol converting device.

CONSTITUTION: A protocol converting part 15, etc., consisting of information equipment 11 provided with a CPU, etc., and a protocol data base communicates with the external device 12 by a transmission line 13 through the option adapter 16 to convert the non-unified shape connector provided in a standard interface 14 into the unified shape connector. Through this interface system, communication with the external devices of different kinds such as a disk device or a local area network (LAN), etc., can be realized by using one set, at least, of the standard interface board without providing a peculiar interface for every external device.