Secure access telephone extension system and method

摘要

A method and system is provided for conducting secure power line carrier communications in full duplex over the power lines of a building. Power line carrier current telephone extension systems utilize 1) a single BASE unit per central office line (for interfacing line carrier signals with the central office line) and 2) one or more EXTENSION units, one for each extension phone set (for interfacing said line carrier signals with said extension phone sets). The method employs system control logic for providing A) multiple extension arbitration logic, B) privacy from eavesdropping and C) security from third party central office line capture by means of a digital messaging system in each base and extension unit utilizing a unique and matching security key (preamble) with each message instructing the system to change operating states, such as, A) during a conversation an extension unit may be put on hold so that a second matching extension can pick up the line, B) a base unit rings matching extension units to signal an incoming call or C) an outgoing call is initiated by a user taking a matching extension phone off hook to access the central office line. Matching of the random security codes may be initiated by the user. By this means unauthorized access to the central office line (especially for long distance calls) and eavesdropping by other users in the same building with similar line carrier telephone extension products is prohibited.