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[scott kelley]

I was told by someone that it is common to
get erroneous X-10 commands on the power
line.  He said specifically that B-1
commands are common "ghosts".  I saw that
one of the recent updates to AHP corrected
an error which caused the Activity Monitor
to show activity that wasn't actually
occurring.  Is this what he was seeing, or
is there actually a problem with "ghosts"?
If this is a problem, does it occur more on
certain house codes?

Thx
Scott Kelley

[donald mcmow]

Sometimes line noise can be interpreted as
a valid command even though it isn't. You
might find upon investigating that the
problem occurs at a particular time or when
a specific electrical device turns on or
off. The only way to verify if that is the
problem is to check every electrical device
in your home and make sure it is not the
culprit - this could be caused by your
fridge, furnace, stereo, tv, vcr, computer
flourescent lights or even be coming from
outside your home (your neighbours). If
this is a problem then you can get
equipment to condition the power coming
into your home or filters to place on
individual devices.
Sometimes a sequence of line noise is
interpreted as a command and can cause
inadvertant activations if a module/macro
is addressed to the mis-interpreted
address. This could cause you a lot of
missing hair - take things easy and make
changes to your program to see if this is
the case. The solution does present it's
self given time and patience.

[roger1818]

Donald:  Powerline noise can cause false
commands, but it isn’t as common as you
would think since X10 uses "Manchester
encoding" (each bit is followed by its
compliment).  Thus 1-0 is interpreted as 1
and 0-1 is interpreted as 0.  From this you
can conclude that you will never get more
than two 1’s (or two 0’s) in a row (that is
why the start code is defined as 1-1-1-0).
Thus for noise to be detected as an X10
command, it needs to be detected as 1-1-1-0
followed by 18 (half) bits of data where no
more than 2 sequential bits are either 0 or
1.

Probably the most common command noise
could generate would be “J Status
Request.”  This is defined as follows (in
half bits):

1-1-1-0-1-0-1-0-1-0-1-0-1-0-1-0-1-0-1-0-1-0

[X10 Pro]

Powerline noise creating phantom X10 commands
is pretty uncommon, as Roger and Donald point
out. There's no reason that B1 would be more
likely to appear than any other command address.