Remote call for access authorisation to subscriber terminal - is made from appts. with memory contg. secret algorithm for computation of password using serial number obtd. from terminal memory

摘要

A bidirectional link between a remote calling station and the subscriber terminal is established when a number is called and the remote control unit (STFAG) reads the serial number and other data from the memory (SPTE) of the called terminal. The same control unit employs a locally memorised algorithm to compute the access authorisation (password) from the serial number read from the terminal's memory, and to display it visually and/or by speech synthesiser and loudspeaker at either end of the link. ADVANTAGE - Serial number which is different for each subscriber terminal encodes access authorisation so that no additional memory is necessary for limited number of callers to be able to compute it.