With the introduction of DCC only lighting Kits it enables you to have extra control of the locos lighting set-up.
To give the most realistic running you can independent control the;
Rear (red) Lights if you are pulling a rake of rolling stock.
Main Headlights, so when you press the light function the marker lights will come on and then press the function to engage main lights.
if you wish to use one and not the other then there is a switch on the board which can be switched off.
To View a video of how it works please click here https://www.youtube.com/watch?v=rGtfYaJbSfw
*Please be sure that the decoder has the capability to run these additional function
Wiring is kept simple in that you have the 3 main connections of Blue, Yellow, and white and then to independently control these functions take the function wire from the decoder and solder it onto the labeled tab depending on what function you wish that to control.