Any one of a plurality of terminals sharing the same number determines whether
or not to switch a transfer to any of the other terminals sharing the same number.
If it determines that the transfer is to be switched, it authenticates one terminal
among the other terminals sharing the same number, and then outputs a transfer
switching request according to the authenticated terminal to a communication control
station. The communication control station performs a transfer switching process
concerning the authenticated terminal based on the transfer switching request outputted
from the first terminal.
