PURPOSE: To prevent an exchange from being large-sized and expensive by selecting a remote station to a stand-alone function when communication between a master station and the remote station is disabled and connecting an emergency call from a subscriber accommodated in the remote station to a specific subscriber accommodated in the remote station.

CONSTITUTION: A photoelectric conversion circuit E/O in a remote terminal station equipment RT connecting to a central terminal station equipment converts an optical signal into an electric signal and sends the signal to an interface circuit IF. Then an act signal selection circuit ASEL selects the act system in a duplicate route and a subscriber is connected from a subscriber circuit interface circuit SLCIF via a stand-alone selection circuit SSEL. When a stand-alone request signal due to a fault of a transmission line is received by a control circuit CTL from the act selection circuit ASEL, the control to realize the stand-alone function is implemented. When the control circuit CTL detects an emergency call, subscribers S1, S2 are connected to specific subscribers X1, X2 to attain the talking. Thus, the large sized and expensive system is avoided.