EXCHANGE

PURPOSE:To attain the registration for an incoming transfer service for a user from an optional telephone set by collating pass word information received by a reception circuit with pass word information stored in a storage circuit corresponding to subscriber information from the reception circuit. CONSTITUTION:A collation circuit 103 reads a pass word corresponding to subscriber information from a reception circuit 102 from a storage circuit 104 and collates it with pass word information from the reception circuit 102. When two sets of the pass word information are coincident as a result, it is discriminated to be a legal subscriber and subscriber information and registered information are outputted to an information transmission circuit 105. On the other hand, when the pass word information is dissident, it is discriminated not to be a legal subscriber, no information is sent to the information transmission circuit 105 and the registration is stopped. When it is discriminated to be a legal subscriber as the result of collation, the subscriber information and the registered information outputted to the information transmission circuit 105 are sent to the service memory control device 11 from the information transmission circuit 105 as above the registered in a service memory 9 through a controller 11.