PURPOSE: To improve the reliability of a data transfer by executing an error check of a received block, transferring a data block as it is to a transmitter by infrared rays if it is correct, comparing the transferred data block with a correct data block, transferring its correct data block to a receiver again by infrared rays if there is an error, and transferring a data part by restoring the infrared rays even if the infrared rays are cut off temporarily.

CONSTITUTION: One data block of a transmitting signal is transferred from a transmitter 3. If the received data block is a definite format, a receiver 4 sets its data part 12 to a buffer of the inside, and transfers the data buffer just as it is to the transmitter 3. The transmitter 3 compares the data part 12 sent from the receiver 4 with the data part which is sent previously, and if they are equal to each other, it is discriminated that the transfer is executed correctly, and the next data block is transferred. If they are different from each other, the previous data block is transferred to the receiver 4 again.