PURPOSE: To transfer an incoming to a transfer sender extension telephone set automatically to a destination extension telephone set being a destination of an extension telephone set operator by utilizing the convenience of absence transfer as it is, and dialing a number from the destination extension telephone set so as to apply destination display of the extension telephone set operator to a destination display device.

CONSTITUTION: The extension operator hooks off a handset of a transfer destination STA12 and connects the call, then dials a destination transfer registration code. Then the extension telephone set of the own seat, that is the extension number of a sender extension telephone set (sender STA) 11. An outgoing register (OTR) 6 receiving all of the dial information transmits dial information in a route shown in the figure of a central controller (CC) 4. Further, the destination, that is, allocated position information of the destination STA12 is transmitted also to the CC4. When the CC4 analyzes the dial information and recognizes that it is the destination transfer display request, a recorder (MEM) 5 is utilized by using an extension number of the sender STA11 of the own seat to be dialed, it is converted into the allocated position information of the sender STA11, and the allocated position information of the destination STA12 being the destination is converted conversely into the extension number of the destination STA12 by using the MEM5 similarly.