PURPOSE: To eliminate the need for redialing from this side by registering the on-seat wait request to a caller even when the caller is in absence registration and the connection is disabled to attain callback when the caller releases the absence registration.

CONSTITUTION: A personal computer 1a is provided with a presence management table 10 and an on-seat wait request terminal management table 11. A caller subscriber B makes a call to a subscriber A registered on the table 10 and recognizes it that the subscriber A is absent. In this case, a table 11 is retrieved by registering an on-seat wait request when the subscriber A leaving its seat returns and the absence registration is released, Then whether or not the waiting subscriber B to the subscriber A of absence registration is registered is retrieved. When the registration of the subscriber B is recognized, callback to the subscriber B is automatically implemented. When the subscriber B replies, the connection request to the subscriber A is executed.