PURPOSE: To provide an extension number position registration device in a switchboard capable of easily registering the extension line number of an extension line terminal all time.
CONSTITUTION: Plural extension terminals 4-1 to 4-n are connected to the local switchboard via respective line circuits 2-1 to 2-n, and these extension terminals are assigned logic number, respectively. When the desired extension number and an access code indicating a registration request are inputted through any of the extension terminals 4-1 to 4-n, the extension number and the access code are passed to a central processing unit 9 via a line circuit. In answer to this, the central processing unit 9 registers the extension number in a storage part 11 corresponding to the logic number assigned to the extension terminal. When the extension number is designated after it was registered, the central processing unit 9 reads the logic number corresponding to the extension number out of the storage part 11, identifies the terminal device based on the read logic number and executes an exchange control.