Tom, to answer and confuse you some more...
If you are familiar with cell phones and calling out of state, you "roam" or "ride" on another service provider in that area so that is how you would connect with 911. If you are from FL and you are in TX and dial 911 you would be riding on texas' service so it would connect w/911 there. To confuse the piont more, when you do dial 911 you are directed towards the STATE POLICE not local city police. This has been a problem for them since they are inadated w/calls and its not their area. The state police have no idea were you are you have to tell them and then they connect you with the local police in that area. I have done this a few times, witnessing car accidents, one theft, and some other stuff. Its a great service and I would no sooner want to leave my cell phone @ home than my permit and gun. Hope this helped.