PURPOSE: To omit the read control program of the data processing unit consisting of plural readers by using the AND signal between a message signal and a transfer preparation completion signal for it as a response signal to readers.

CONSTITUTION: When an error signal is outputted from the message signal output end of reader 1a, this error signal passes through inverter 12 to close AND circuit 11. The transfer preparation completion signal outputted from reader 1a for the error signal is not supplied to data processing unit 9. Meanwhile, the error signal and the transfer preparation completion signal are outputted through AND circuit 13. This output signal is supplied to reader 1a as a response signal for the transfer preparation completion signal above. Reader 1a stops the transfer preparation completion signal and transfers to the next read operation. As a result, the response signal is supplied automatically in each reader independently of data processing unit 9.