what does the "distance sensor" do ?

i'm looking at my wiring diagrams and pulling apart my speedo,

there is a "distance sensor" in the back of the speedo. It looks alot like a glass fuse.

What's it here for? I'm trying to figure out if im going to need to reinstall it or not?

On my 750LTD it was for sensing the distance traveled after turning on a turn signal. Once reaching the preset distance, the turn signal would turn off all by itself.

bingo, thats exactly what its for.