To provide an exchange system for closing a line after a call is set to an on-hook state, if there is a busy call when a fault occurs in a transmission facility, and to provide a method for forcibly closing the line.

An exchange station A 10 has an exchange A 11 and a transmitter A 12, and an exchange station B 20 has an exchange B 21 and a transmitter B 22. The transmission facility 30 connects the station A 10 and the station B 20 via individual line signal methods. When a fault occurs in the facility 30, the transmitter A 12 receives a notification signal via an individual line signal and sends a signal for clearing back the busy line. The exchange A 11 processes the clearing-back, releases the call, and sends the notification signal. The transmitter A 12 receives the notification signal, sends a signal to the exchange A 11 to forcibly close the line. This line closing process is conducted similarly in the station B 20.