To enable a user to use an optional CT terminal included in a network in his own log-in name by using a controller which controls a security information answer device and the calls and a maintenance operation device which is connected to a server and sets the security information in a data base.

A security information retrieval device 25 retrieves a password corresponding to a log-in name out of a data base 22 storing the security information with the log-in name used as a key. A security information inquiry device 23 inquires of another server about the security information if the desired security information is not contained in its own data base. A security information answer device 24 returns the inquiry result of the security information. A call controller 26 controls every device and the calls. Then a maintenance operation device 27 is connected to a server 21 and sets the security information in the data base 22.