Communicating over power lines

• US 3,909,821 A
• Filed: 10/04/1973
• Issued: 09/30/1975
• Est. Priority Date: 10/04/1973
• Status: Expired due to Term

• Current Assignee: Trust C.O. American
• Original Assignee: Howard S. Baker, Klaus Kubierschky, Neil H. Jagoda
• Inventors: Kubierschky, Klaus, Jagoda, Neil H., Baker, Howard S.
• Primary Examiner(s): Habecker, Thomas B.
• Application Number:
  US05/403,512
• Time in Patent Office: 726 Days
• Field of Search: 340/31R,31A,150,171
• US Class Current: 375/259
• CPC Class Codes: H04B 2203/5433 Remote metering
• CPC Class Codes: H04B 2203/5445 Local network
• CPC Class Codes: H04B 2203/545 Audio/video application, e.g. interphone
• CPC Class Codes: H04B 2203/5483 using coupling circuits
• CPC Class Codes: H04B 2203/5491 using filtering and bypassing
• CPC Class Codes: H04B 3/54 Systems for transmission via power distribution lines

Abstract

An audiofrequency signal is applied to a power amplifier having an output impedance of considerably less than an ohm that is coupled through a network comprising at least a capacitor that presents a low impedance to this audiofrequency signal and much higher impedance to energy at the 60 Hz power frequency to a power line to provide an amplified signal that is transmitted to a receiver separated from the transmitter by at least one distribution transformer and having a high pass filter for rejecting the 60 Hz power frequency and a number of harmonics thereof while transmitting the audiofrequency signal. The system is especially advantageous for using ordinary power lines for transmitting information in connection with automatic meter reading.

Claims

1. Apparatus for communicating over power lines carrying power at power frequency comprising, a source of an audiofrequency signal within a predetermined frequency range within the frequency range of 1 kHz to 20 kHz, power amplifying means having a low output impedance coupled to said signal source for amplifying said audiofrequency signal, output terminal pair means for connection to a power line, and means for coupling said output terminal pair means to said amplifying means, said means for coupling having an output impedance presented to said output terminal pair means within the range of 0.1 to 4 ohms within said predetermined frequency range and a much higher impedance at said power frequency.

2. Apparatus for communicating over power lines in accordance with claim 1 wherein said output impedance presented to said power line is substantially less than 2 ohms at the frequency of the signal provided by said source.

3. Apparatus for communicating over power lines in accordance with claim 1 wherein said means for coupling comprises an inducator in series with a capacitor forming a circuit exhibiting series resonance substantially at the frequency of said audio-frequency signal.

4. Apparatus for communicating over power lines in accordance with claim 1 and further comprising first and second power lines carrying power at power frequency connected to said output terminal pair means.

5. Apparatus for communicating over power lines in accordance with claim 4 and further comprising, detecting means coupled to remote power lines at a remote point for detecting the signal provided by said power amplifying means, and at least one power distribution transformer intercoupling said remote power lines with said first and second power lines for transmitting through said transformer the amplified signal provided by said power amplifying means.

6. Apparatus for communicating over power lines in accordance with claim 1 wherein the frequency of said audiofrequency signal is within the range of 3 kHz to 8 kHz.

7. Apparatus for communicating over power lines in accordance with claim 6 wherein the frequency of said audiofrequency signal is substantially 5 kHz.