Backup Switch Question

[Craven93]

I have a 1972 C10 with a 350 engine and a 3 speed Muncie (Three on the tree). There is a switch at the base of the column that turns on the reverse lights. I had to adjust it to get them working correctly.

Ive been tearing things apart over the winter to do a little needed work. I pulled the transmission and replaced all the seals. While putting it back together, I was looking at the switch that's attached to the side cover. It's obviously a reverse switch of some kind, but I'm curious what exactly its for. There is only one wire going to it. It's difficult to trace it out at the moment, as I have the truck up in the air.

Anyone have a quick answer of what it's for and how exactly it works? I've included pictures of the two different switches as well as the 1 wire plug for the transmission one.

Thank you in advance.