<Tr> <Td> </Td> <Td> This section needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (February 2018) (Learn how and when to remove this template message) </Td> </Tr> <P> Enhanced 9 - 1 - 1 (E-911 or E911) automatically gives the dispatcher the caller's location, if available . Enhanced 9 - 1 - 1 is available in most areas (approximately 96 percent of the U.S.). </P> <P> In all North American jurisdictions, special privacy legislation permits emergency operators to obtain a 9 - 1 - 1 caller's telephone number and location information . This information is gathered by mapping the calling phone number to an address in a database . This database function is known as Automatic Location Identification (ALI). The database is generally maintained by the local telephone company, under a contract with the PSAP . Each telephone company has its own standards for the formatting of the database . Most ALI databases have a companion database known as the MSAG, Master Street Address Guide . The MSAG describes address elements including the exact spellings of street names, and street number ranges . </P> <P> In the case of mobile phones, the associated billing address is not necessarily the location to which emergency responders should be sent, since the device is portable . This means that locating the caller is more complicated, and there is a different set of legal and technical requirements . To locate a mobile telephone geographically, there are two general approaches: to use some form of radiolocation from the cellular network, or to use a Global Positioning System receiver built into the phone itself . Both approaches are described by the radio resource location services protocol (LCS protocol). Depending on the mobile phone hardware, one of two types of location information can be provided to the operator . The first is Wireless Phase One (WPH1), which is the tower location and the direction the call came from, and the second is Wireless Phase Two (WPH2), which provides an estimated GPS location . </P>

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