To reduce cost by eliminating the need for a fault detection circuit in the multiplex communication equipment contained in a joint box and to avoid the waste in the replacement of an input circuit at the sometime on the occurrence of an output circuit attended with a fault of various loads.
An output circuit 41 for driving and switching loads, where a fault by an external factor is liable to take place, is excluded from a 1st multiplex communication equipment 22 contained in a joint box 21 integrally and then is built into a 2nd multiplex communication equipment 25 which connects a communication line. A defective factor of the 1st multiplex communication equipment 22 is decreased for eliminating the need for replacement, and on the occurrence of a fault in the output circuit 41, only the 2nd multiplex communication equipment 25 to which the input circuit 23 is not mounted is replaced.
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SUMITOMO ELECTRIC INDUSTRIES