| 摘要 |
PURPOSE:To connect an incoming call to a caller via a main link by setting an extension telephone set number to be connected for incoming call corresponding to a trunk line trunk, calling a corresponding extension when an incoming call is given to the trunk line trunk and allowing said extension to hook off. CONSTITUTION:Extension telephone set numbers are preset to a memory 7 corresponding to the trunk line trunks. When an incoming call is given to a trunk line trunk 1 (#0), a central controller 2 identifies an extension telephone set (extension number 200) 4 to be called which is to be connected by a stored data in the memory 7 and transmits a call signal 5 to the extension telephone set 4 from a line circuit 3. When the extension 4 to be called hooks off in order to respond to the incoming call, the off-hook is detected by the line circuit 3 and transmits response information to the central controller 2. The central controller 2 stops the call signal 5 to the line circuit 3 and returns a response signal to the trunk line trunk 1 by closing a DC loop in the own station so as to close a channel of a main link 6. |
