04479033 is referenced by 103 patents and cites 14 patents.

A power line telephone extension system for carrying electrical signals between a subscriber's telephone line of a conventional telephone communication system and the subscriber's remote transmit-receiver device, (such as a conventional extension telephone), over the AC electric power wires available to the subscriber which includes: master linking circuits for processing signals between the subscriber's telephone line and the AC power wires; extension linking circuits for processing signals between the AC power wires and the subscriber's remote transmit-receive device, such as a conventional extension telephone; and a directional coupler circuit electrically coupling the remote transmit-receive device and the telephone line. The extension system is quite suitable for use with the presently available, well known, conventional extension telephone that plugs in by the plug (modular or 4 prong) provided therewith, to the directional coupler. Thus, the extension phone can then be used along with the extension linking circuits at any location at the subscriber's premises where there is access to the AC power wires.

Title
Telephone extension system utilizing power line carrier signals
Application Number
6/363063
Publication Number
4479033
Application Date
March 29, 1982
Publication Date
October 23, 1984
Inventor
Robert T Dunn
Bedford
MA, US
William M Brown
Acton
MA, US
Agent
Hamilton Brook Smith & Reynolds
Assignee
Astech
MA, US
IPC
H04M 11/00
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