Complex sentence: Basic locomotive decoders provide control of speed and direction while supplemental function decoders control headlights, ditch lights, or movable non-traction components such as remote-controlled pantographs.
Split into simpler sentences: Basic locomotive decoders provide control of speed and direction. Supplemental decoders can be placed into a locomotive, to control headlights, ditch lights, or movable non-traction components such as remote-controlled pantographs.