9-1-1 System Processes


  • 9-1-1 is mostly called from a wireless device. The Nine Eleven National Association (N.E.N.A) shows that “An estimated 240 million calls are made to 9-1-1 in the U.S. each year. In many areas, 70% or more are from wireless devices.”

There are different process for 9-1-1 calls:

Basic 9-1-1:

  • Basic 9-1-1 means that when the three-digit number is dialed, a call taker/dispatcher in the local public safety answering point (PSAP), or 9-1-1 call center, answers the call.The emergency and its location are communicated by voice (or TTY) between the caller and the call taker.

    Enhanced 9-1-1:

    In areas serviced by enhanced 9-1-1, the call is selectively routed to the proper PSAP for the caller’s location, and the PSAP has equipment and database information that display the caller’s phone number and address to the call taker. 93% of counties with 9-1-1 coverage have enhanced 9-1-1 for callers. The term “enhanced 9-1-1” is not synonymous with wireless 9-1-1.

    Wireless Phase I:

    When Phase I has been implemented, the call taker automatically receives the wireless phone number.This is important in the event the wireless phone call is dropped, and may allow PSAP employees to work with the wireless company to identify the wireless subscriber.Phase I also delivers the location of the cell tower handling the call. The call is routed to a PSAP based on cell site/sector information.

    Wireless Phase II:

    While this is the ideal of that phase of 9-1-1 according to the USA today operators give as a testimony that “There are times when it doesn’t come up at all. Every day we receive calls where we get a tower address and that’s it.”

  • Phase II allows call takers to receive both the caller’s wireless phone number and their location information.The call is routed to a PSAP either based on cell site/sector information or on caller location information.

    9-1-1 Calls through VoIP:

    Business and residential use of Voice over Internet Protocol (VoIP) telecommunications services is growing at a rapid pace.Methods to bring 9-1-1 calls into E9-1-1 systems have recently become available, and NENA is leading work to develop full E9-1-1 capability for VoIP-based services.

    Next Generation Trends:

    Estimates are that nearly 29.7% of all U.S. households currently rely on wireless as their primary service as of June 2011 (having given up wireline service or chosen not to use it). (CTIA – Wireless Quick Facts – Dec 2011)

Technology behind the current 911 system.

Source: http://www.greatcall.com/greatcall/lp/technology-behind-911-calls-infographic.htm
Source: http://www.greatcall.com/greatcall/lp/technology-behind-911-calls-infographic.htm

Source: https://www.nena.org/?page=911Cellphones