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Sub-Carrier Multiplexing

Discussion in 'Electronic Design' started by Jimbo, Jun 15, 2006.

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  1. Jimbo

    Jimbo Guest

    Does anyone have any ideas on how to place a signal on an AC line that
    runs inside a 4,000 square foot house? Generally, how do you put the
    piggybacked signal onto the line? (sub-carrier multiplexing) What is
    the typical bandwidth on such a system? I'm interested in doing this
    but I don't want to play around too much with an AC outlet too much.
    I've heard about very simple systems that transmit two bits each cycle.
  2. Luhan

    Luhan Guest

    Yes, its called X-10. Sold by Radio Shack and others for remotely
    turning things on and off. They send multiple copies of each command
    signal to improve the odds of one of them getting thru. Not exactly
    reliable for sending data.

  3. Jimbo

    Jimbo Guest

    I'm familiar with X-10, I was thinking about making my own interface
    board, of course as long as I check to make sure there are no patents
  4. have a look at the philips semicon site, they have/had some powerline
    data ics.
    The app notes had the calcs for the LC isolation circuits. Havent
    investigated this for a coupleyears, so the chips may be in dodo land

  5. Luhan

    Luhan Guest

    (please learn to bottom post)

    For all practical purposes, patents only really apply to commercial
    uses. You could model a system after the X-10 signals since they were
    designed to propogate over the AC lines. Circuits for both sending and
    receiving are available from Microchip among others.

  6. Jim Thompson

    Jim Thompson Guest

    You can even make an *exact* copy of an X10 device for your own use.

    The defining law concerns itself with *profiting*.

    For instance, until fairly recently, it was perfectly legal to build
    your own cable decoder box. The cable companies ultimately convinced
    state legislatures to make laws defining theft of cable *service*.

    ...Jim Thompson
  7. John Fields

    John Fields Guest

  8. Joerg

    Joerg Guest

    Hello John,

    However, X-10 is a rather crude AM protocol. Carrier on/off. I am using
    it since about five years and I am not enthused, would never use it for
    anything beyond convenience functions. It only works when it wants to.
    Turn on the margarita blender and it chops up all the commands along
    with the ice cubes.
  9. John Fields

    John Fields Guest

    And, as such, if the intent of making the copy is merely to enjoy
    the benefits of the invention without paying the owner of the patent
    their just dues, that's prohibited.

    However, building a copy for study, without payment to the owner of
    the patent, is allowed, in the hope that that study will lead to
    advancement in science and, ultimately, the betterment of mankind.
    Was that a bad thing?

    Your electric company spent a lot of money to run copper all the way
    from their alternators to your home, the deal being that (usually)
    you wouldn't have to pay for the copper to be run, but that you'd
    pay for every watt-hour you used, and that they'd make their money
    on the come.

    The cable company does the same thing with coax, but invoices

    The intent is the same, however, and that's to provide you with a
    service for which you agree to pay.

    If you build a Zbox in order to fool the watt-hour meter into
    thinking that you're you're using less energy than you are, then
    you're a liar and a thief.

    Same thing with the cable company.

    Check with your wife.

    Since she's Jewish, she'll know the difference between right and
  10. Jim Thompson

    Jim Thompson Guest

    Wrong! I've had lengthy discussions with my patent lawyer over this.
    You have to *profit* in the *sale* sense to infringe. "Enjoyment"
    only counts with cable TV converters because of their cable-specific
    No. I was just pointing out that factoid.
    In that case you *are* using the device to steal something. With X-10
    your use doesn't steal anything.
    But not patent infringement with "build-one" of anything else for your
    own use.
    My wife is not Jewish, she simply has a biblical name. However my
    daughter-in-law (Duane's widow) is Jewish.

    But I know right from wrong... it's alright to tar and feather a
    leftist weenie, but not a Republican ;-)

    Might be alright to tar and feather Texans as well ;-)

    ...Jim Thompson
  11. Joel Kolstad

    Joel Kolstad Guest

    Because it would have been far better if they had spent all the money they
    handed to lobbyists to get the law passed to instead just put decent crypto
    into their cable system in the first place. Not to mention it would have
    been just as easy to *contractulally* disallow cable TV descrambling -- why
    in the world do we need a *law* regarding it?
    The usual argument is that, "if there's a signal on my line, unless you,
    say, want to *contractually* only let me use some of it, I should be able to
    do with it what I want" -- can you imagine the power company charging you a
    different price for the electricity to run that margarita blender of yours
    vs. light bulbs? I'm sure someone would like that idea, and with today's
    technology it could certainly be done.

    Truth me told, though, I'm a lot more disgusted with the legislation that
    made it illegal to intercept AMPS cell-phone calls than anything having to
    do with cable TV -- this strikes me as a law that mainly had the effect of
    delaying truly secure wireless phone calls for consumers. Thanks a lot!

  12. Jimbo

    Jimbo Guest

    Mr. Thompson, please consult an attorney before you follow your own
  13. John Fields

    John Fields Guest

  14. John Fields

    John Fields Guest

    Nope. Tell your lawyer that he needs to get over to:

    and read:

    "35 U.S.C. 271 Infringement of patent.

    (a) Except as otherwise provided in this title, whoever without
    authority makes, uses, offers to sell, or sells any patented
    invention, within the United States, or imports into the United
    States any patented invention during the term of the patent
    therefor, infringes the patent."

    Seems pretty clear to me...

    True, but I thought you were advocating copying an X-10 box for
    personal use thinking the patent was still in force. Weren't you?
    Wrong. Go to:

    and read it for yourself.
  15. Not to me, not without reading what is "otherwise provided
    in this title".
  16. John Fields

    John Fields Guest

  17. John Fields

    John Fields Guest

  18. Jim Thompson

    Jim Thompson Guest


    You confuse* written law with case law. Find me a one-off that was
    successfully prosecuted... unless, of course, its use committed a real
    "crime", such as stealing cable "services".

    * As most people do who are not regularly involved in patent
    litigation, as I am.

    ...Jim Thompson
  19. Jim Thompson

    Jim Thompson Guest


    The USPTO has become a national joke... they'll issue Letters Patent
    to anything that walks in the door.

    And "35 U.S.C. 27" *wasn't* created by the USPTO.

    Also, the USPTO doesn't enforce patent law.

    ...Jim Thompson
  20. John Fields

    John Fields Guest

    **** you, you arrogant ass. No one was talking about case law; the
    claim you made was that it's legal to copy an invention for
    personal use.

    It isn't, you were wrong, and puffing yourself up isn't going to
    change that.
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