ki for the general public communication - management mode

摘要

A telecommunications security device for use on the communication medium includes a first (10) and a second (11) security unit each arranged to be inserted into for example the telephone line (12) adjacent a user device (13,14). Each unit includes a separable memory module (225) with all the modules having a memory (212) storing identical information. The information stored includes a plurality of pairs of random signals one of each pair providing a request signal and the other the security code. The central unit on receipt of a telephone call provides a signal requesting an ID code from the remote unit and on receipt of the ID code issues from one of the pairs the security code request signal. On matching the received code with the expected code a transmission gate is opened. The pairs are used in turn until all of the pairs have been used whereupon an indicator shows this condition. The modules (225) can be removed and the memory 212 re-written with fresh pairs of codes. The module includes a security logic circuit (211) which controls access to the numbers to a fixed set of access rules allowing authentication and/or encryption and providing security against unauthorized access.