| 摘要 |
PROBLEM TO BE SOLVED: To detect abnormality on a balances transmission line. SOLUTION: Concerning the multiple dwelling house intercom system, in which living room machines installed in respective houses, a multiple dwelling entrance machine installed in a multiple dwelling entrance or the like, a control room base unit and a controller installed in a caretaker's room or the like are connected through the balanced transmission line, at least one of living room machines, controller, multiple dwelling entrance machine and control room base unit is provided with signal confirming parts 61 and 81 for detecting abnormality on the balanced transmission line by comparatively detecting two unbalanced signals, for which calling signals or balanced signals of speaking voices are converted, received through the balanced transmission line when performing calling/speaking among the living room machines, multiple dwelling entrance machine and control room base unit through the controller.
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