History of 911

THE FIRST 911 CALL was made from a telephone in Haleyville, Alabama on February 16, 1968.

The 911 concept is very simple:

Recognize when the numbers 9-1-1 are dialed from any telephone
Allow no-coin calls from pay telephones
Route the call to the jurisdiction where the call is originated
Display the caller's telephone number & location in the communications center.

The technology behind 9-1-1 is of performing this concept takes many forms. However, there are some basic building blocks.

First, telephone companies already maintain a subscriber database listing every assigned telephone number, the subscriber's name, address and billing information.
Second, the telephone system already identifies the telephone number for every call placed, in order to properly bill the subscriber each month.
A 911 system adds a third component to the system---a Master Street Address Guide (MSAG). This database cross-references every assigned telephone number, subscriber's address (the near universal use of cell phones has impacted the methods by which the 911 call center establishes the caller's location - see below) and the block number ranges for every street, in every jurisdiction served by the telephone company.

The location, administration and structure of the MSAG is different among the various regional and independent local telephone companies. Some companies maintain local databases, while others maintain just one or two database sites for their entire, multi-state territory. In either case, the ability to send data at the speed of light means that transactions occur very quickly.

Fourthly, most telephone company have built special switches and networks to carry 911 traffic, so that other telephone company traffic will not intefere with 911 operations, and 911 traffic is protected from power failures and other system problems.

Now, when a caller dials 9-1-1, the call is recognized by the telephone company central office switch and routed to the 9-1-1 network. The caller's telephone number is immediately associated with the caller's address and other information.

Next, the call is processed -- sometimes simultaneously -- to obtain the ID code of the agency that should handle the call. The 911 network then routes the voice and caller information to the correct agency. The caller information is displayed when the call-taker answers and, at some agencies, the call information is printed out when the call is completed.

At most agencies, a 9-1-1 call may be transferred to another Public Safety Answering Point (PSAP) or to any seven-digit number. If a 9-1-1 call is transferred to another PSAP, the previously acquired information is transferred along with the voice call, so the other call-taker can also view the information.

In foreign countries, in fact, they've adopted other digits for reporting emergencies. As of 1992, the European Union has mandated that its member states adopt 112 as their emergency number, but allowed participating countries to operate that number simultaneously with their previous three-digit emergency number.

Cell Phones & 9-1-1

Courtesy of USA Today, 4/23/2007

Wireless E911 systems fall into two categories. Each has its pluses and minuses.

Network-based

How it works: Uses information from multiple cell sites to get a location fix on callers.

Plus: Works well in urban markets, which tend to have a lot of cell sites. Also reliable inside office buildings and other places where cell sites have been installed.

Minus: Doesn't work well in rural areas, where cell sites can be few and far between.

Who uses it: Cingular, T-Mobile

Consumer tip: Be prepared to give a reasonably good description of your surrounding sand give your wireless number to the dispatcher so they can call you back.

Global Positioning System (GPS)

How it works: Uses information beamed from low-orbiting satellites to pinpoint the location of callers. Works off GPS chips built into handsets.

Plus: Works well in rural settings where satellite signals can't easily be blocked.

Minus: Less reliable in urban markets where skyscrapers, office buildings and other structures can block satellite signals. Weather can also be an issue.

Who uses it: Verizon Wireless, Sprint

Consumer tip: Make the call where you have a clear view of the sky. If you're calling 911 from indoors, get close to a window.

USA Today, 4/23/2007


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