Mobile phones can be used in countries with different emergency numbers. A traveller visiting a foreign country does not have to know the local emergency numbers, however. The mobile phone and the SIM card have a preprogrammed list of emergency numbers. When the user tries to set up a call using an emergency number known by a GSM or 3G phone, the special emergency call setup takes place. The actual number is not even transmitted into the network, but the network redirects the emergency call to the local emergency desk. Most GSM mobile phones can dial emergency calls even when the phone keyboard is locked, the phone is without a SIM card, or an emergency number is entered instead of the PIN. Most GSM mobile phones have 112, 999 and 911 as pre-programmed emergency numbers that are always available.<sup id="cite_ref-IETF_0-0" class="reference">[1]</sup> The SIM card issued by the operator can contain additional country-specific emergency numbers that can be used even when roaming abroad. The GSM network can also update the list of well-known emergency numbers when the phone registers to it. Using an emergency number recognized by a GSM phone like 112 instead of another emergency number may be advantageous, since GSM phones and networks give special priority to emergency calls. A phone dialing an emergency service number not recognized by it may refuse to roam onto another network, leading to trouble if there is no access to the home network. Dialing a known emergency number like 112 forces the phone to try the call with any available network. On some networks a GSM phone without a SIM card may be used to make emergency calls and most GSM phones accept a larger list of emergency numbers without SIM card, such as 112, 911, 118, 119, 000, 110, 08, and 999. However, some GSM networks will not accept emergency calls from phones without a SIM card, or even require a SIM card that has credit. For example, Latin American networks typically do not allow emergency calls without a SIM. Also, GSM phones sold in some countries like Singapore do not accept 112 as an emergency number even if they have a SIM card inserted. The GSM phones may regard some phone numbers with one or two digits as special service codes. It might be impossible to make an emergency call to numbers like 03 with a GSM phone. In the United States, the FCC requires networks to route every mobile-phone and payphone 911 call to an emergency service call center, including phones that have never had service, or whose service has lapsed.<sup id="cite_ref-FCC_wireless_1-0" class="reference">[2]</sup><sup id="cite_ref-FCC_payphone_2-0" class="reference">[3]</sup> As a result, there are programs that provide donated used mobile phones to victims of domestic violence and others especially likely to need emergency services. Mobile phones generate additional problems for emergency operators, as many phones will allow emergency numbers to be dialed even while the keypad is locked. Since mobile phones are typically carried in pockets and small bags, the keys can easily be depressed accidentally, leading to unintended calls. A system has been developed in the UK which connects calls where the caller is silent to an automated system, leaving more operators free to handle genuine emergency calls.<sup id="cite_ref-3" class="reference">[4]</sup>
Just be careful when traveling in foreign countries, if you dial 112 you will be transfered to the nearest local emergency services. So, you need to know the basics about the local language. But, yes it works even if the keypad is locked.
Since we're on the subject, if I were to be traveling through Mexico into Guatemala, Belieze, and much of Central America, should I buy an unlocked throw away phone here and then prepaid SIM cards in a given country? Or depend on my iPhone 4 to connect me in an emergency?... I'll be using skype for communication with home for the most part... which wont be much, but I'd like to have the option to make a "local" call as much as cell coverage will allow at any given time.
I did some reading on Snopes.com and found there is some misinformation about this. Some people were believing that it increased cellphone strength. This is not true. It wont help if you are trapped in a mineshaft.
Don't assume that there will be ubiquitous cell coverage or that 911/112/999 is universal - in some areas, dialing 911 will route you to a telephone operator who will need to ask you questions and then direct your call to the nearest emergency responders. I am amazed at the number of people who seem to think that all they need in an emergency or if they get lost is their cellphone - it's a helpful tool, but should never be one's only means to get out of trouble.
