thunderbirl

In my newly acquired 2008 ML350, while looking for an answer to the "switched" power outlet question (which I do understand, now) , I came across the two position fuse 113a/113b in the box under the hood. It looked like the arrangement in the E350 that allows you to swap the power outlet from switched to constantly on.

I've read (from the fuse allocation list) that this fuse is for the horn.

Can anyone tell me why a horn has two positions for the fuse??

Thanks.