Telephone extension system utilizing power line carrier signals

Abstract From the Canadian patent

An extension telephone system communicates with a conventional subscriber telephone line where the subscriber's line telephone is located, through available AC power wires which carry signals that may be modulations of RF carrier frequencies and which are coupled to the power wires. Incoming telephone line signals are detected and modulate a first RF carrier frequency which is coupled to the AC power wires at the line telephone location and these signals are coupled from the AC power wires at an extension telephone location and, demodulated and fed to an extension telephone which is energized by DC power derived from the AC power wires at the extension location. The extension telephone …