A standard-SIP (session initiation protocol) protocol control module and an expanded sip protocol control module are provided so as to correspond to respective Sip protocol corresponding terminals, such as wireless LAN terminals compliant with the SIP. A signal (a request) from each Sip protocol corresponding terminal is converted into a signal according to a protocol of an IP-PBX and is sent to a PBX basic-connection-processing providing module. A signal (a response for the request or a request to the Sip protocol corresponding terminal) from the PBX basic-connection-processing providing module is converted into an Sip protocol signal and is sent to the Sip protocol corresponding terminal. A location-information management module collects a basic service set identifier (BSSID) from each wireless LAN network and stores the BSSID information into a database.