The quotes around the word real are there because this idea acts like real Rule 17. But since we don’t have 3 position rotary switches on our throttles, it’s not quite the same.
Here’s how it works on the throttle (after you’ve done the hard part–the work):
If you have a locomotive headed out on the road with a train, assuming your headlights are off, push the Headlight button and F7. The headlight on the front of the engine will come on. The lights on the rear will stay off. Take your train out. If you feel the need to dim your headlight, press Headlight. When you want it bright again, press Headlight. With this setup, you will be toggling back and forth between bright and dim. That is exactly what you would be doing in real life.
Thus you can dim a bright headlight at will with this system. And the lights at the other end of the loco will stay dark. Because they are on different buttons, and have not been turned on.
If you reverse the direction of this train, the lights will stay as you have left them. That is, if you have a bright headlight, and you back up the train, the headlight will stay bright. And the lights on the other end of the loco will stay dark.
Should you wish to run around the train and pull it back to the yard, you will press Headlight to dim, and press F7 to off. The front headlights will then be off. Then press F8 and F9. You’ll then have a bright headlight on the other end of the loco. Which can be dimmed at will.
Now let’s say you want to use that same loco to switch the yard. Assuming the lights are off, you hit F7 and F9. The lights at each end of the unit will be dim, presuming that’s what the yardmaster wants in his yard. And they will stay that way until you decide they should be different. Direction of travel will have no effect.
The si