I know that the serial data output is for activating railsounds.
But what exaclty is the output from the serial data pin?
What volatage?
Is it a pulsed signal?
Does the feature code determine what the serial data output is?
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The serial data is a TTL (o-5V) logic level 8 bit data serial stream at around 3000 BPS. I forget the exact bit rate it's an odd number related to the clock speed of the R2LC processor or the 455khz TMCC carrier. Jon told me, and I forget which one it was tied to. 
Thanks John.
So when in conventional mode, how does a railsounds board know the difference between serial data or DC offset for activating whistle or bell?
Take a ERR RailsoundsCommander for instance.
One of those can be installed in a conventional loco, with no R2LC, and sounds will be activated by DC offset.
But when using a R2LC with TMCC, sounds are activated with serial data.
That has been explained before on by Jon Z. The RS knows when TMCC is present and would ignore the DC off sets. G
I see GGG beat me to it. A TMCC locomotive that doesn't have any TMCC signal on the tracks will also operate in conventional mode and react to the offsets.
