Enhanced 9-1-1

9-1-1 History

The origin of 9-1-1 can be traced back to England, 1937. England was the first country to use a national three digit emergency number. If you were witness to an injury accident in England, dialing 999 would put you in contact with emergency service personnel.

Some 20 years later in 1958, the International Association of Fire Chiefs advocated for a national emergency number in the United States. However, it was not until 1968 that 9-1-1 was brought to reality through the coordination of AT&T and emergency service providers, resulting in AT&T making the digits 9-1-1 available for national use. This event marked the beginning of the growth of emergency number associations and professional organizations.

While this was a major step towards decreasing emergency service response time, 9-1-1 technology did not yet have the ability to tell the 9-1-1 operator who the caller was or from where the call was originating. This is where Enhanced 9-1-1 (E9-1-1) stepped in to provide many enhancements over Basic 9-1-1.

Some features of E9-1-1

- Automatic Number Information (ANI) When you call 9-1-1, the telephone number you are calling from is automatically displayed to the 9-1-1 call-taker.

- Automatic Location Information (ALI) Supplies the name and address associated with the calling telephone number. Additionally, police, fire, and EMS agencies that are assigned to the caller's location are displayed to the 9-1-1 call-taker.

- Selective Routing (SR) The most time saving feature of an E9-1-1 network. SR automatically routes the call to the appropriate PSAP (Public Safety Answering Point) based on the callers location, which eliminates the need for manual routing by a 9-1-1 call-taker.

Call routing when you dial 9-1-1

- When a 9-1-1 call is made it travels over the public telephone network to the telephone company's central office (CO). At the CO it is recognized as a 9-1-1 call and routed through a high-speed dedicated 9-1-1 network to a specially equipped phone switching office.

- Once at the switching office, known as a tandem, the telephone number (ANI) of the incoming call is queried in a database. The resulting information provides routing instructions for the 9-1-1 call to the appropriate PSAP along with the caller's telephone number.

- As the 9-1-1 call-taker answers the call, 9-1-1 equipment in the PSAP queries another database, retrieving the location information (ALI) and displays both ANI and ALI to the 9-1-1 call-taker simultaneously. All of this is done without human intervention.

Check out this image that shows the route a 911 call takes from the time you dial til an operator answers.

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