Switch inside key

So the range on my keys are a bit shakey at best but before I prise them apart I'm curious as to what the little screw-switch is inside the key recess.

Its labeled LOCK and UNLOCK and is currently set to LOCK.

My key is the black flip out three button type, lock unlock and boot switches.

It unlocks the tray that holds the battery.

Oh I see! That bit falls out!