Private branch exchange system

A private branch exchange system comprising:

• a user's mobile cellular apparatus;
• and
• a private branch exchange that includes a communication path between connected telephone sets and a communication path between the telephone sets and a public switched telephone network,
• the mobile cellular apparatus including
• position measurement part that locates a current position of the mobile cellular apparatus and a response part that transmits the current position, as a user current position, which is located by the position measurement part in response to a position confirmation request from the private branch exchange,
• the private branch exchange including
• user information in which user identification information that identifies the user, mobile cellular apparatus identification information that identifies the user's mobile cellular apparatus, and an extension telephone number of a telephone set to be used by the user when he/she sits at his/her desk are registered in an association manner,
• schedule information in which date/time information that is indicative of a scheduled date/time for a conference and a conference position at which the conference is to be held are registered in an association manner,
• layout information that includes an in-premises layout and installation information that is indicative of how the telephone sets are installed,
• a user status determination part that transmits, when receives a user designated incoming call, the position confirmation request to the mobile cellular apparatus identified based on the mobile cellular apparatus information of the user information, and
• an incoming call control part that forwards, if the user current position received from the mobile cellular apparatus is different from the schedule information, an incoming call to a near-user-installed telephone set having an extension telephone number based on the user current position and the layout information.