| 摘要 |
PURPOSE:To attain the operation confirmation of a standby communication control unit in the standby state by providing a loopback circuit to a level converter side end of a signal lien tying the standby communication control unit and a level converter. CONSTITUTION:A main controller 1 controls the standby communication control unit 5 via a bus signal line 9, selects a selector 22 via a control circuit 29 and controls the level converter 6 via control lien 16 an activates the loopback circuit 32 via a control circuit 33. A data is sent from the standby communication control unit 5 in this state, a loopback data is received by the circuit 32 to collate the data thereby confirming the propriety of the data transmission/ reception just near the line. Then the selector 23 is selected by the control circuit 29 to apply the propriety communication for the data transmission/ reception the line similarly to the line controller 3.
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