[no subject]

Too bad the Monterey doesn't log events because someone might be able to
catch a a valid single frame transmission among all the BSC's if it were
possible to capture the reams of data the Monterey produces under such
conditions.  I wonder if I can put a macrocam on the display and feed the
image into an optical scanner with OCR.  It should be able to see each
update of the display and then I'd just text search the resulting document
for letters other than BSC.  Oh great, another damn project.  If only I had
grad students slaves!  (-:

If the funky power supply can trick the Monterey into reporting bad strings
of X-10 signals to the point of differentiating such noise as X-10 1 or 0
bits, it's already half-way to the point of creating something that can
trick a much dumber lightswitch to activate.

I understand that there's error-checking built-in the X-10 protocol, but
it's pretty primitive.  I also understand that there are plenty of
impossible things that happen all the time.  Who would have thought light
pieces of foam could do enough damage to the shuttle to bring it down?
Until they ran the tests and they saw the pictures and examined the damage
very closely, there were plenty of engineers and rocket scientists who went
on record with great conviction to say it was impossible.

I guess the only person who can make the determination of why those lights
lit for certain is Bruce, since he's got the magic power supply, the light
switches in question and a means to further analyze the situation: the
Monterey.

Sadly, most threads about bad X-10 devices usually end here with the
application of a filter because most people just want to get their system
back to working order.  I doubt many people would want to sit around in a
dark house next to a Monterey analyzer waiting for a light to turn on
randomly so they could freeze the display when it happened to see what was
coming down the wire at the time.

Maybe Bruce will buy a replacement and send the magic supply to you for
further analysis so you can see on the scope what's happening.  It would be
nice to know for sure because reports like this seem to turn up with
regularity.  Maybe he'll give us the exact model number of the PS so anyone
so inclined to investigate further could buy their own.

So I guess these are all "questions for the ages."  I'm still troubled by
why the activations are so infrequent if the noise level is constant.
Perhaps the power supply produces noise irregularly at different points in
its operation cycle.  Or maybe by saying "random" Bruce did imply that they
were activating incorrectly fairly rapidly.   Knowing the switch make/model,
the rate of activation, the PS's proximity to the affected switches, the
noise level at those switches and the strength of the noise emanating from
the PS would all be very useful items in determining the true nature of the
interaction.

As far as I can tell, no one claims that Manchester encoding is highly
resistant to errors.  AFAIK, it was used by X-10's designers mainly to save
bandwidth.  At least that's how ACT's Phil Kingery describes it:

http://www.act-solutions.com/kingery18.htm

<<Since the X-10 protocol is limited in baud rate by the very sine wave
itself (either 60Hz or 50Hz on this planet), the X10 engineers could not
afford to include sophisticated checksums, nor cyclic redundancy checks or
even a parity bit to increase dependability. They only had two ways to do
it. First, they used what is called "Manchester encoding". That meant that
every "1" bit was actually sent with its complement, or 1+0. Every "0" bit
was sent with its complement, or 0+1. This greatly increased the reliability
of the data frame since single-bit errors were quickly identified and the
data frame could be discarded.>>

Without parity bits or CRC checking, I'm not sure how error-resistant the
X-10 protocol truly is, especially when "attacked" by 5 million random bits*
per day.

The bottom line is still "get a meter and a box of X-10 filters" if you want
to keep your X-10 running smoothly.  I'm a little surprised that the noise
overwhelmed the XTB, but I assume the PS was located fairly far from the
XTB.  I also never realized how difficult a good repeater is to design until
I read the Kingery article about preset dims and the changes X-10 made to
the protocol in midstream.

--
Bobby G.

*5,184,000 bit at 60Hz times 60 seconds times 60 minutes times 24 hours.
Granted, that has to be divided by eleven for a sequence of bits to
constitute a single, valid X-10 frame, so the number drops to 471272.