The
emergency number for
America is usually
911. Many
cell/
mobile phones automatically dial it (or the
local emergency number when you press and hold the
9 key. Obviously, opportunities for accidently doing this abound.
My phone also makes it more difficult to hang up, once the emergency number has been dialed -- it requires a separate set of keystrokes to hang up an emergency call. You cannot just press the END key.
Most cell carriers consider emergency calls to be free. They do not bill airtime for emergency calls, and emergency calls are often possible even when the phone is otherwise locked.
Finally, it has been my experience that American phone switching systems will connect you to 911 if you play with the switchhook too much. I was testing a phone line, lifting the receiver often. Once when I lifted the phone, I didn't get a dialtone -- I got a 911 operator instead! In a panic, I hung up on her, but she promptly called back. I was able to explain to her that everything was okay, and I wasn't actually trying to signal for help with a paperclip and some bare phone wires.
In the US, the feature that allows the 911 operator to call you back, and even send emergency services to your address, is called Enhanced 911.