RETRANSMISSION CONTROL SYSTEM

PURPOSE:To prevent a transfer call from being transferred to an unexpected party by adopting the constitution that an incoming transfer call to a destination is not transferred again when the transfer destination makes another transfer registration. CONSTITUTION:When an incoming call is given from a subscriber 1-1 to a subscriber 1-2, an exchange 2-2 transfers the information representing the subscriber number of the transfer destination 1-3 and the presence of transfer call to an exchange 2-3 so as to transfer the call to the exchange 2-3 accomodating the subscriber 1-3 being the transfer registered destination of the subscriber 1-2. The transfer is executed via a central controller 3-2, a common signal line controller 4-2, a common signal line 5-2, a common signal line controller 4-3 and a central controller 3-3. On the other hand, the exchange 2-3 uses the information being the transfer call from the exchange 2-2 being a transfer sender and the information that the subscriber 1-3 of the own station is under transfer registration so as to discriminate the retransfer disable state and returns a busy tone to the subscriber 1-1 being the sender via a line.