A system comprising an external device and an intercom system to be used in a housing complex constituted by a plurality of dwelling buildings (A-E), wherein the intercom system comprises, within each of the plurality of dwelling buildings (A-E): a dwelling parent device installed in each dwelling, a terminal device (10, 20) configured to perform a calling operation for calling the dwelling parent device, and a building control unit configured to communicatively interconnect the dwelling parent device in each dwelling of a host building and the terminal device (10, 20) by way of an intercom line (L1, L2, L3), wherein the external device comprises: a storage unit in which a predetermined application is installed, a display unit configured to display the predetermined application, a communication interface configured to form a first signal transmission path between the external device and a setting server through an external network, and to form a second signal transmission path between the external device and the terminal device (10, 20) or the building control unit through a wireless communication, and a control unit configured to activate the predetermined application so as to establish communication between the terminal device (10, 20) or the building control unit and the setting server, the system being characterized in that the control unit is further configured to activate the predetermined application so as to determine whether the setting server has terminal information to be transmitted to the terminal device (10, 20) or the building control unit, and to receive the terminal information from the setting server via the external network without storing the terminal information into the external device and transmit said terminal information to the terminal device (10, 20) or the building control unit via the wireless communication when it is determined that the setting server has said terminal information. wherein the intercom system comprises, within each of the plurality of dwelling buildings (A-E): a dwelling parent device installed in each dwelling, a terminal device (10, 20) configured to perform a calling operation for calling the dwelling parent device, and a building control unit configured to communicatively interconnect the dwelling parent device in each dwelling of a host building and the terminal device (10, 20) by way of an intercom line (L1, L2, L3), a dwelling parent device installed in each dwelling, a terminal device (10, 20) configured to perform a calling operation for calling the dwelling parent device, and a building control unit configured to communicatively interconnect the dwelling parent device in each dwelling of a host building and the terminal device (10, 20) by way of an intercom line (L1, L2, L3), wherein the external device comprises: a storage unit in which a predetermined application is installed, a display unit configured to display the predetermined application, a communication interface configured to form a first signal transmission path between the external device and a setting server through an external network, and to form a second signal transmission path between the external device and the terminal device (10, 20) or the building control unit through a wireless communication, and a control unit configured to activate the predetermined application so as to establish communication between the terminal device (10, 20) or the building control unit and the setting server, the system being characterized in that the control unit is further configured to activate the predetermined application so as to determine whether the setting server has terminal information to be transmitted to the terminal device (10, 20) or the building control unit, and to receive the terminal information from the setting server via the external network without storing the terminal information into the external device and transmit said terminal information to the terminal device (10, 20) or the building control unit via the wireless communication when it is determined that the setting server has said terminal information. a storage unit in which a predetermined application is installed, a display unit configured to display the predetermined application, a communication interface configured to form a first signal transmission path between the external device and a setting server through an external network, and to form a second signal transmission path between the external device and the terminal device (10, 20) or the building control unit through a wireless communication, and a control unit configured to activate the predetermined application so as to establish communication between the terminal device (10, 20) or the building control unit and the setting server, the system being characterized in that the control unit is further configured to activate the predetermined application so as to determine whether the setting server has terminal information to be transmitted to the terminal device (10, 20) or the building control unit, and to receive the terminal information from the setting server via the external network without storing the terminal information into the external device and transmit said terminal information to the terminal device (10, 20) or the building control unit via the wireless communication when it is determined that the setting server has said terminal information.