| 摘要 |
PURPOSE:To detect all suboffice being faulty rapidly only by transmitting a call signal once to all subordinate stations successively by noticing that the possibility that all subordinate stations are faulty decreases more and more as the number of the subordinate stations increases more and more. CONSTITUTION:In a conventional testing circuit 4 for the answer of a calling suboffice, all-suboffice-unanswering detecting circuit 4d, an AND gate 4e, and an all-suboffice-faulty storing and display circuit 4f are provided. The detecting circuit 4d is set by a call signal from a suboffice calling circuit 1 to the 1st suboffice, and reset by an answer-presence detecting circuit. Therefore, the state of the detecting circuit 4d is stored in the storing and display circuit 4f via the AND gate 4e at timing delayed slightly behind test timing for a final suboffice #n; when this circuit 4f is in a set state, all suboffice are judged to be faulty and when in a reset state, at least one of the suboffice is judged to be normal. In the said reset state, every suboffice is checked successively as before. |
