E911 stands for Enhancned 911. It is a solution that allows VoIP users to be connected to emergency services personnel (such as police, ambulance and fire department) by dialing 911 on their physical or virtual phones, just as if they were using a regular landline.
Why is there a need for a special 911 solution?
Regular landlines are, by nature, definded by a physical location and are registred to customers with a specific name and address. Landlines are routed by PSTN - Public Switched Telephone Network. The PSTN can therefore easily route calls to the office of Public Safety Answering Point nearest to the caller, where an operaor will connect the caller to the appropriate agency.
VoIP numbers (and also cellular numbers) on the other hand are not bound by a physical location. A VoIP number can be used to make a call from anywhere in the U.S or the world. VoIP uses the internet for most part rather than the telephone network. Addionaly the ability to use different caller IDs with VoIP and it
a service that is provided by an access network provider to provide location information to users of the network. To do this, it uses knowledge of network topology and a range of location determination techniques to locate devices that are attached to the network. The precise methods that are used to determine location are dependent on the type of access network and the information that can be obtained from the device.