SUBSCRIBER IDENTIFYING SYSTEM FOR PUBLIC TELEPHONE NETWORK

PURPOSE:To easily decide the validity of a subscriber terminal by performing the arithmetic operation of an identification code received at a center device side, and comparing a computed result with a received computed result. CONSTITUTION:When outgoing is issued from the subscriber terminal 1, a subscriber identification signal sending device 2 is connected to a center device 4 via a public telephone network 3, and after that, a subscriber identification number and the result of computation of the number are sent to the center device 4 in a PB signal. The center device 4, when receiving the signal, applies the same arithmetic operation as that applied on the device 2 to the identification number, and decides the validity of a call by comparing the computed result with the received computed result, and performs call disconnection and logging processing, etc., on a malfeasant call. Thereby, it is possible to easily decide the validity of the subscriber terminal.