Relative vs Absolute Speed Steps

CAB1 is unlimited steps, it's relative to wherever you are from the previous step.  R100 mode is really just CAB1 with some changes to how the Legacy display works, throttle graph, keypad icons, etc.  TMCC is 32 step with positive control, not relative steps.  Legacy is 200 step mode positive control and Legacy 9-bit code transmission.

"positive control" refers to the fact that TMCC or Legacy speed step #nn will always give you the same speed setting to a locomotive.  Relative means it just adds an increment to the previous last speed setting.

To dumb it down some, one can think of relative steps as pressing the channel Up and Down buttons on a TV remote, and absolute steps as pressing the numbers for the channel you want.  If you hold down the channel up button for a couple seconds, you have no idea what channel you'll end up on, where as if you type in channel 07, you'll always end up on channel 7.  It's useful for Legacy and other command systems to know exactly how fast an engine is moving, especially for things like recordings using the sensor track.  

To the best of my understanding, with absolute speeds, the cab1L and legacy systems can provide smoother transitions when changing speeds and more responsive control than the relative steps used in the original Cab1 control.  On the other hand some products will only work with relative steps.   

JGL

Makes perfect sense now. Thank you. 

So for us Legacy new guys, is there a correlation between the speed steps and actual mph(in scale I guess)?  For example when the speed button is pushed and normal speed selected, my GS4 Daylight goes to speed step 145. Certainly, this is not 145mph(even tho 'ol 4436 is kickin it pretty good). Where do I find the scale mph?

TedW posted:

So for us Legacy new guys, is there a correlation between the speed steps and actual mph(in scale I guess)?  For example when the speed button is pushed and normal speed selected, my GS4 Daylight goes to speed step 145. Certainly, this is not 145mph(even tho 'ol 4436 is kickin it pretty good). Where do I find the scale mph?

This link was given in another post and has the speed step/ smph conversion. 

https://sites.google.com/site/...fo---lionel---legacy

BPARS, thx

JohnGaltLine posted:

To the best of my understanding, with absolute speeds, the cab1L and legacy systems can provide smoother transitions when changing speeds and more responsive control than the relative steps used in the original Cab1 control.  On the other hand some products will only work with relative steps.  

It's my understanding that the CAB1L only does relative steps.  It would be useful to hear from someone like Jon Z. to confirm that.

gunrunnerjohn posted:

It's my understanding that the CAB1L only does relative steps.  It would be useful to hear from someone like Jon Z. to confirm that.

That would make more sense,  but I've heard people here on the forum state that the cab1L gives better speed control than the original cab1, so not sure how that works if it is issuing the same commands.  

JGL

Interesting point, I think we'll have to wait for Lionel to give us the straight scoop.