OnStar Question

I saw a TV ad for the OnStar (sp?) system the other day. The one where this guy locks himself out of his GM car in the middle of nowhere. Fortunately (for him) he has his cell phone so he calls somebody and from some control room somewhere (it looks like Mission Control in Houston) they push a button and his car doors magically unlock. Neat trick.

But my question is this. I know how GPS works but how does someone remotely unlock his doors? Does the Satellite send a signal to his car? Does his car have a dish hidden somewhere.

And what would happen if he was stick in the middle of a tunnel? At first I thought it had something to do with cellular phone cells but that doesn’t work in the middle of nowhere…

So how does this trick work?

IIRC, my Yukon Denali owners manual says it is tied into the cell phone. I didn’t get onstar with mine, but it still came with a cell phone antenna any way, and there are plug-ins for the cell phone in the center console to add it. SO I would guess that if you were too far out, it may not work.

Apparently it does depend on cellular phone cells. From the official OnStar web site (http://www.onstar.com):

Emphasis is mine. So, it is dependant on cellular coverage being available. Don’t lock yourself out in the middle of nowhere…