Telephone extension system utilizing power line carrier signals

US3949172A · kind A · utility

Inventors

• William M. Brown · Beaverton, US
• John Ruddy · Sudbury, US
• Robert T. Dunn · Bedford, US

Key dates

• Filing date: Feb 8, 1974
• Grant date: Apr 6, 1976
• Expiry date: Feb 8, 1994

Classification

• Technology area (CPC H): Electricity
• CPC primary: H04B2203/5437
• WIPO field: Telecommunications
• WIPO sector: Electrical engineering

Abstract

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 produces extension telephone signals which modulate a second RF carrier frequency which is coupled to the AC power wires at the extension location and this modulated carrier is coupled from the AC power wires and demodulated at the line telephone to produce the extension telephone signals in suitable form for applying to the telephone line. Thus, telephone calls to the subscriber's line telephone can be received by the extension telephone and calls to the telephone extension telephones can be connec…