To obtain a superior central monitor system, where a nonvolatile memory on a control controller cannot be rewritten due to mis operation of a management computer of an operator.

A write enable/inhibit setting switch En is provided on a control controller Cn. When the write enable/inhibit setting switch En is set to a permission mode, when the controller Cn receives a write request to a nonvolatile memory Dn from a management computer A, the controller Cn informs the management computer A of transition to a write mode, and data transmitted from the management computer A are written in the nonvolatile memory Dn. When the write enable/inhibit setting switch En is set inhibition, when the controller Cn receives a write request from the management computer A, the controller Cn rejects the write request and informs the management computer A that no transition of the write mode of the nonvolatile memory Dn will take place.