it's built into most phones - even dumb phones. You don't need data or anything to make the 911 call (but it does need to be charged up - duh) - found this out when a battered womens shelter came looking for phones to donate for their clients who could not afford service.
I will probably screw this up a bit but I am no mood to look up FCC regulations.
Here in the US, all carriers must provide the ability to access E911 regardless
of service to the phone. Essentially, when the phone is in an SOS state it is
"off network"
E911 still works because by the FCC the phone must be able to
use any available network and 911 calls must be able to override
everything that determines how normal voice calls are processed.
If anyone else can flesh that out better, please take a whack at it.
I will probably screw this up a bit but I am no mood to look up FCC regulations.
Here in the US, all carriers must provide the ability to access E911 regardless
of service to the phone. Essentially, when the phone is in an SOS state it is
"off network"
E911 still works because by the FCC the phone must be able to
use any available network and 911 calls must be able to override
everything that determines how normal voice calls are processed.
If anyone else can flesh that out better, please take a whack at it.
The other answerers are mostly correct, a cell phone without an active plan can still call 911. What was left out, is that a cell phone that does not have signal, i.e it does not see a repeater or sattelite, CANNOT call anything. There is no way for the RF link to go through. It will not magically reach the emergency line. So, if you are lost in the middle of the Andes, with no cell phone connection, it won�t do you any good. You can�t call what your signal doesn�t reach.
