| 摘要 |
PURPOSE:To improve the reliability of a data transmission system by providing a mistransmission preventing means to prevent such a case where a central unit transmits the untransmitted change terminal data on a reading terminal already stored in a memory means for change terminal data to a host computer. CONSTITUTION:A transmission and flag FD is set into the change data in order to prevent the misjudgment of a host computer 1. Then the flag FD is set for the untransmitted change data in case this data contains the change data on a terminal whose registration is cancelled as a change terminal or if the past untransmitted change data on the change terminal is detected when a central unit 3 receives a request from the computer 1 for the terminal data on the present time point of the change terminal earlier than the change data. Thus the transmission of the change data is inhibited to the computer 1. This improves the reliability of a data transmission system.
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