PURPOSE: To attain quick and sure restoration at a fault of dial connection control by allowing a connection controller to send a signal for starting the restoration to parallel processing systems simultaneously after on-hook by a caller and a called party is confirmed.

CONSTITUTION: A base station or an exchange informs interrupt of processing to a connection controller. The connection controller gives a command to the base station such that the base station should send a message urging on-hook to a portable telephone set and gives a command to the exchange such that the exchange should send a message urging on-hook to a called party. Then the base station informs an on-hook of the caller and the exchange informs the on-hook of the called party to the connection controller respectively. The connection controller sends a restoration signal to each parallel processing system to give a command of starting the interruption of the processing and of restoring the state to a state before the processing operation start to each parallel processing system. Thus, quick and sure restoration after the connection of the communication is implemented and the convenience of the user, operability and the reliability of the system are improved.