Freewire programming with X10

[Knightrider]

In a nutshell,

X10 RF devices (motion detectors, rf remotes) default to HC "A" when the batteries die out, hence the avoidance of "A".

If you break the code wheels off of a device, it reverts to HC "M", hence the avoidance of "M".

When you start up a computer which is connected to a CM15A, the x10nets service will send "P16 ON", hence the avoidance of HC "P".

FWIW,  I use all of those HC's, and get along just fine.

[dave w]

Another FWIW,

I agree with Brian and Knightrider. I have used X10 since 1979, and when dabbling in Automation with an early controller in 1987, I was using ALL 16 house codes (not all unit codes within each HC however). NO particular house code ever was any more problematic that the others.

$0.02
I use house code A, in fact I use A1 as a main light in the bedroom. If the light ever comes on when it isn't supposed to, I know I have a motion sensor that needs battery attention....works good 

[Brian H]

Sometimes we think alike. A1 for a light would give you an indication a motion sensor was not on its assigned address anymore.
Address P16 is one to not use unless you need an indication x10nets has started.
I believe P16 is also used by the Leviton X10 tester.
My Smarthome 1132CU Advanced Controller Screen shows a PHail Acknowledge when my XTBM does its power on check for a repeater.

[eagle]

Great tip/suggestion dave.

I think I'll use that. 

r,
eagle