Abstract: Method and apparatus for detecting an authorized tap on an electrical power line in which electrical reflectometry signals are supplied to a portion of the power line by a transmitter, reflected such signals are received from the power line by a receiver and the reflected signals are compared in a comparator with signals reflected by authorized taps on the power line to determine whether or not unauthorized taps are present. In a preferred embodiment, the transmitter and receiver are part of power line communication apparatus and, if desired, such apparatus can transmit signals indicating tap changes to a remote control center.

Abstract: Power line communication method and apparatus in which data modulated radio frequency carriers from two different sources are transmitted by the power line, the range of frequencies of the carriers from one source partially overlapping the range of frequencies of the carriers from the other source, and in which carriers of the one source are shifted to frequencies other than the overlapping frequencies when carriers at the overlapping frequencies and from the other source are present on the line. Optionally, the data signal sampling rate can be changed to simplify signal filtering requirements.