Sub-Carrier Multiplexing

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.

Luhan

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

martin

(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.

Luhan

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

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.

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 laws.

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

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!

---Joel

Mr. Thompson, please consult an attorney before you follow your own advice.

Jim Thomps>

Not to me, not without reading what is "otherwise provided in this title".

John,

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

Bwahahahahaha!

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