The objective of the invention is to make it possible, by simply reading a code (30) by use of a mobile terminal (10), for a setting necessary for utilizing the mobile terminal (10) as a cordless handset to be automatically made with respect to a relay apparatus (20) that connects to a fixed telephone line (300). The mobile terminal (10) analyzes the read code (30) and thereby acquires information necessary for pairing with the relay apparatus (20) through Bluetooth, and then sets the information in the mobile terminal (10). The mobile terminal (10) then connects to a call control server (400) via a wireless LAN, generates a registration ID and a password necessary for a call, sets the generated registration ID and password in the mobile terminal (10) itself, and registers the registration ID and password with the call control server (400). The mobile terminal (10) then transmits the registration ID and password to the relay apparatus (20) by use of Bluetooth connection. The relay apparatus (20) sets the rece
