It used to be that when there was an emergency, such as a car accident, someone might go inside the house to call for an ambulance.
Now in that situation you go outside the house, to make sure you get a clear signal.
Hmmm...
Tom
P.S. Remember when people would say things like, "Could I use your phone?" and you'd walk them to the room in the house with the phone?
In California, if it's a real emergency and a land line is available, you should use it. The call centers that handle 911 calls from cell phones have longer response times than the ones that handle POTS calls.