Envoy Government Communications Newsletter

How Does E911 Work?

You'll be surprised with how many computers, networks, and people are involved in answering an Enhanced 911 (E911) call. Don't let your knowledge stay stranded any longer. Our step-by-step chart walks you through the path your call takes from the moment you ring 911 to the point the ambulance comes to your rescue.

	1. The user places a wireless call, which transmits the caller's voice and his or her number to the closest tower.
	2. The tower transmits the caller's voice signal, the wireless phone's callback number, and the tower's ID code to a mobile switching center. The mobile switching center assigns a unique 10-digit routing number to ID the call, and groups the information into three different electronic packets to send to three different receptors.
	3. Notified of the emergency, the position-determining system uses GPS satellites to find the caller's location, sending latitude/longitude location data to a location information database.
	4. The local exchange carrier receives the voice signal and the 10-digit routing number. The routing number alerts the local exchange carrier that the call is an emergency, and the carrier's 911 switch decides automatically which emergency call center is appropriate and assigns the call.
	5. At the appropriate emergency call center, an operator receives the 911 voice call and a computer receives the unique 10-digit routing number. Using the routing number, the computer searches the location information database and retrieves the caller's wireless number, the tower's address, and the caller's exact latitude/longitude coordinate location. Meanwhile, a computer mapping application uses the latitude/longitude data and maps directions to the caller's location.
	6. The operator dispatches emergency response team to save the day.

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