PURPOSE: To make it possible to change transmission definition information by a central monitor device and to improve operability by updating the transmission definition information managed by the monitor device and loading down the updated information to its corresponding gate way when IF data between the monitoring device and another control device are changed.

CONSTITUTION: A transmission information managing part 14 in the central monitor device 1 sets up, updates and stores the transmission definition information 18 for a gate way 6a (6b) through transmission system control parts 7, 13 and a transmission network 5, and then loads down the information 18. A data processing part 9 edits data based upon the updated and registered information 18 and executes processing such as text conversion. Namely data transmission is mutually executed among control devices 2a, 2b and the device 1 through transmitting and receiving processing parts 10, 11 and the network 5 based upon the information 18 changed by the device 1. Consequently the information 18 for respective gate ways 6a, 6b can be updated and concentrically monitored from the center and the operability can be improved.