V-Start (CV2) allows you to tell the decoder how much voltage to provide at speed step 1. This allows you to program it so the loco will crawl on the first speed step. The value you program into this CV is relative only to the percentage of voltage available to the decoder. For example, a value of "01" provides 1/255th of the available voltage while "02" provides 2/255ths of the available voltage. Since the G-scale setting provides more voltage on the track than N scale, this means that any given value will provide more voltage in G scale than it will in N scale.

Basically all this means is that the higher the value you place in CV2, the more voltage will be provided at speed step 1. If your loco doesn't run on speed step 1, it needs a higher value. If it runs too fast on speed step 1, CV2 needs a lower value. Regardless of the value used for speed step 1, all other speed steps above #1 will be stretched up proportionately to make a smooth ramp all the way up.

V-Max (CV5) allows you to set the maximum voltage the loco will get when on the highest throttle setting. This allows you to set the loco's maximum speed at full throttle. The default value of zero ("00") disables this CV, providing full voltage at full throttle. Values above zero work similarly to V-Start (CV2) - the higher the value, the faster the loco will go at full throttle. Obviously, if the loco won't go fast enough at full throttle with this CV disabled, the highest setting can't make it go faster than it can go. Regardless of the value used for the top speed step, all other speed steps below that will be stretched proportionately to make a smooth ramp all the way down.

V-Mid (CV6) allows you to set the amount of voltage the loco will get when on the middle speed step. Without this CV, there would be no speed curve - just a straight ramp from the value in CV2 to the value in CV5. With CV6, you can make a curve to suit your needs. Most people make a low-belly curve. This provides finer speed-step control at the lower speed steps where it's needed, and a greater increase per speed step at road speeds where that's needed. Regardless of the value used for the middle speed step, all other speed steps below and above will be stretched proportionately to make a smooth ramp from speed step 1 to the middle, and from the middle to the top speed step.

Note: V-Mid may not work (depending on the decoder) unless CV5 is set with a value greater than zero.

For years, only V-Start was implemented, usually for all speed steps . A few years ago, V-Max and V-Mid were implemented for the 14- and 28-speed-step modes. Only recently have manufacturers started implementing all three of these CVs for all three speed-step modes.

Considering that using V-Start, V-Mid, and V-Max is a very easy way to produce a custom speed curve that most people will use, and the User-Loadable Speed Table is something that most people don't want to bother with, I've always wondered why most decoders have always had the User-Loadable Speed Table, but most did not have these three simple CVs implemented for the 128-speed-step mode until just recently. For me, this is an enigma.

These are decoder features. Once configured, they will work on any DCC system.

Most decoders have V-Start. Not all have V-Mid and V-Max. Some have V-Mid and V-Max implemented only in the 14- and 28-speed-step modes. Some have them all implemented in 14-, 28- and 128-speed-step modes. If you want these features, you must be sure that they are implemented for the speed-step mode you plan to use.

Train Control Systems decoders have all of these implemented in all current decoders for all speed-step modes.

All Digitrax decoders have all of these in all speed-step modes.

NCE decoders have all of these in the 28- and 128-speed-step modes.

Some Lenz decoders have V-Start and V-Max implemented in all speed-step modes, some don't. At least one has V-Max with all speed steps when Back-EMF is activated, but not when Back-EMF is not active.

Throttle Up! (SoundTraxx) has V-Start, but does not have V-Mid or V-Max implemented. Instead, they provide a variety of built-in speed curves that can use V-Start and the User-Loadable Trims for manipulation.

All of Digitrax's current systems can program any value into these CVs.

V-Start, V-Mid, and V-Max are not intrusive. You do not need to bother with them unless you want to use them.