CV 49 = 64CV 50 = 64
From the SoundTraxx LC Technical Reference Manual: CV 49 sets the Headlight and CV 50 sets the Backup light. Setting Bit 6 in these CVs (value of 64) controls Rule 17 Lighting.
Rule 17 mode converts the headlight and backup light to independent non-directional lights. When this mode is active, the headlight is controlled as if it were FX1 (Function 5) and the backup light as FX2 (Function 6).
Hope this answers your question. This is somehing I had been wanting to do, too, but had not read the technical reference manual.
If I understand their explanation, you will then need to use Function 5 to turn the headlight on and off, and Function 6 for the backup light, instead of the usual Function 0, so those two function keys obviously do not control any of the sound effects.
Here is a link to the manuals.
http://www.google.com/search?hl=en&ned=us&q=SoundTraxx+LC+Technical+Reference+Manual&btnmeta%3Dsearch%3Dsearch=Search+the+Web
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.