Setting up Auxiliary Lighting Functions on the ProtoThrottle

In this video, we explore how to set up the ProtoThrottle to control various auxiliary lighting functions on a locomotive. It’s based on a SD40-2 (thank you ScaleTrains!) with lighted number boards, class lights, and a rotary beacon, but the techniques apply equally well to any DCC equipped locomotive. Keep an eye out for a special treat with the class lights…


  1. On the scaletrains rivet counters with class lights, one can also assign class lights to the ditch light slot if the unit doesn’t have ditch lights, but the headlight or rear light will be on when the ditch lights are white or red but can be off when the lights are off or green. Alternate choices include assigning ground lights or number boards to the ditch switch if there are no ditch/gyra/mars lights. My ESU light control set up looks like

    F.Head = F11 Front light [1] front headlight bright
    F.Ditch = F15 this is the front ditch or mars or gyra light
    F.Dim#1 = F12 Front light [2] front headlight dim
    F.Dim#2 =

    R.Head = F13 Rear light [1] rear light bright
    R.Ditch = F16 this is the rear ditch or mars or gyra light
    R.Dim#1 = F14 Rear light [2] rear light dim
    R.Dim#2 =

    F15 Front ditch/mars/gyra light or beacon
    F16 Rear ditch/mars/gyra light or beacon or class lights
    F17 Beacons and SP UDP emergency red gyralight
    F18 Ground lights, Walkway lights
    F19 Number boards

    I use F0 and F10 to control front and rear lighting when using non protothrottle controls. F0 for front lighting and F10 for rear lighting. Set up across my locos so that when the loco is stopped or going in the opposite direction, the light is dim; bright when moving in the direction the light is facing and the ditch/mars/gyra light comes on automatically. Auxiliary lights are all on F15..F19 for uniformity across all my locos regardless of throttle being used. By sacrificing a few function keys, I can just keep one configuration on my ESU decoders without having to rewrite the CV data on the decoder to match protothrottle or non protothrottle settings.

    Just putting this info out here since it doesn’t look like it has been updated since 2018.

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