PURPOSE: To improve the workability and the efficiency of examination by making such an examination work unnecessary that an inspector brings a magnet for examination close to an interphone device from the outside of a dwelling unit.

CONSTITUTION: Dwelling unit entrance slave machines SQ1 to SQ20 and living room machines AQ1 to AQ20 installed in dwelling units RA1 to RA20, a controller 10 connected to living room machines by a main cable L1, and a manager room machine MQ1 which is connected to the controller 10 by a manager room machine cable L2 are provided, and the manager room machine is provided with a disaster prevention sensor examination instruction sending circuit 1 which outputs a disaster prevention sensor examination instruction f1 to be sent to living room machines and a disaster prevention sensor examination data reception circuit 2 which receives disaster prevention sensor examination data DV corresponding to this instruction, and each living room machine is provided with a disaster prevention sensor examination instruction reception circuit 14 which receives the disaster prevention sensor examination instruction, a disaster prevention sensor SEN1 which is artificially operated by the disaster prevention sensor examination instruction to output the disaster prevention sensor examination data, and a disaster prevention sensor examination data sending circuit 15 which returns this data outputted from the disaster prevention sensor to the manager room machine.