European Emergency Calling

In countries where GSM/UMTS cellular standards are used, dialing a number to report an emergency is focused on the handset, not the telephone network. Software in the handset recognizes the dialed digits, no matter if it's 9-1-1, 1-1-2 or another combination. Based on that the number, the handset tags the call as an emergency, and forwards it to the cellular network.

The network switch recognizes the "emergency" tag, and routes the call based on the country's and local procedures. The call could be routed to the local police, to an emergency call center or some other location for handling.

This method a roamer, particularly a person from another country, doesn't have to know what number to dial. In fact, he/she only has to dial his home country's emergency telephone number, and it will be properly routed.

Some Blackberry GSM handset models take this technique to the next level--they don’t refer to a call as a 9-1-1 call. Instead, they refer to it on the screen as an "emergency call." It make dialing for help that much easier and quicker.  
 
Thanks to Allen Muse of AT&T Mobility for this info.