Abstract: An interface card communicates a scanner with a MACINTOSH computer. The scanner previously sends status value and 8-byte redundant data to the interface card before transmitting the image data. The 8-byte redundant data is not acceptable to the MACINTOSH computer and is converted into irregular image on the screen. In addition to a CPU, a memory, an address decoder, a counter and status registers, a S-to-P converter and an image data receiver, the interface card also has a circuit which consists of four AND gates, four flip-flops and a counter. The scanner sends a step trigger signal *ST and a synchronous signal *AR before sending data to the interface card. Therefore, the circuit processes the *ST and *AR signals and counts the clock pulses for transmitting redundant data so as to delete these data from the interface card.