a monitoring computer for monitoring a facility to be maintained; and

a monitoring center computer for monitoring information held with said monitoring computer and sending maintenance information to said monitoring computer, through a pay station line,

wherein said monitoring computer has a database for storing image data of said monitored facility, and said monitoring center computer includes:

a database for storing CAD data for said monitored facility;

a function for providing coordinates to said image data sent from the monitoring computer to form image coordinate data;

a function for superposing said image coordinate data and CAD coordinate data for said CAD; and

a function for locating a needed maintenance spot on the basis of a result of said superposition processing;

a tag having a storage and being installed in said monitored facility; and

mobile equipment being connected with said monitoring computer through pay station line,

wherein said mobile equipment has:

a function for receiving said tag information via radio communication; and

a function for sending the received tag information to said monitoring center computer,

wherein said monitoring center computer further has:

a database for storing said maintenance information for said monitored facility;

a function for receiving said tag information sent from the mobile equipment;

a function for retrieving said maintenance information from said database on the basis of said tag information; and

a function for sending said retrieved maintenance information to either said mobile equipment or said monitoring computer, or both.