PURPOSE: To eliminate the waste to print different mechanical specification by notifying it to the system by using a system in which a discriminating function for the mechanical specification is provided for the printer itself without disintegrating centro-interface concept.

CONSTITUTION: In a printer 17, when data received are judged to be discrimination code, the data are once stored in built-in RAM. The content of DIP switch preset is read out by the printer 17, and the content of discriminated data is compared with the content set by DIP switch to check whether they are in harmony with each other. When discrepancy is confirmed, fault line on centro- interface is made to active state by the printer 17 and it is notified to the main system. In the main system, due to said reason, the fact that connected printer is different form desired one is recognized and the job is aborted.