Understanding X10 Dims???

[Charles Sullivan <cwsulliv@xxxxxxxxxxxx>]

Using a CM11A to monitor dims (brights) on the power line, I notice
that most X10 transmitters, e.g., CM11A, Mini/Maxi-controllers,
RR501, send dims (brights) according to the formula:
  dims = 11*N + X
where N >= 0 and X varies randomly - usually 2 or 3, sometimes 4.
The CM11A reports a maximum of 210 dims.

The variation in X does not appear to be an imprecision in the
monitoring interface circuitry - two CM11As on line simultaneously
always report identical received values.

A strange thing about X is that a value of 3 or 4 produces _less_
actual dimming than 2.  The effect is difficult to see with a
standard X10 lamp module (and digital RMS multimeter) because of
short term fluctuations in line voltage, but is very dramatic
with X10's LM14A 2-way lamp module.  With the LM14A, a plot of
either extended level (0-63) or output voltage versus received
dims (2-210 dims from the fully ON state) looks like a sawtooth
curve with "tooth height" of as many as 6 extended levels or
almost 10 percent.  (There's a similar sawtooth curve from the
fully OFF state when brights are received.)

Can any of the X10 hardware/firmware gurus on this newsgroup
explain the reason for the variability of X in the transmitted
dims and the strange retro effect of X = 3,4 versus X = 2 on X10
modules?  Thanks for your help.

Regards,
Charles Sullivan