Enhanced 911

When Enhanced 911 (E911) was created in the 1970s, it provided for selective routing, automatic location information (ALI), and automatic phone number identification (AN1) (iCert and 911 Education Foundation, 2015). Selective routing is an E911 feature that routes an E911 call from a control office to the designated primary Public Safety Answering Point (PSAP), which is a call center operated by the local government. At the PSAP, the call is answered by a specially trained official known as a 911 dispatcher. The dispatcher’s computer receives information from the telephone company about the physical address (for landlines) or geographic coordinates (for cell phones) of the caller. This information is used to dispatch police, fire, medical, and other services as needed (Bandwidth, 2019). Selective routing means that if you were traveling from Northern Michigan south on 1-75 to Florida and you placed a 911 cell phone call in any of the six states you would pass through along this 1700 mile journey, your call would be automatically routed to the appropriate local 911 dispatcher.

The Automatic Location Identification (ALI) database makes sure that the dispatcher can determine your geographic location. The ALI is maintained on behalf of local governments by contracted private third parties — generally the Incumbent Local Exchange Carrier (ILEC) under contract by the PSAP. Most ALI databases have a companion database known as the MSAG (Master Street Address Guide). The MSAG provides the exact spelling of streets, street number ranges, and other address elements.

Today, while 911 has become an absolute expected service and is a full partner with police, fire, and medical services, there are professionals in the PSAPs who use, and manage, 911 call centers 24 hours a day (Holdeman,

2010). Helping this to happen is Computer-Aided Dispatch (CAD) (Dempsey, 1999).


CAD is a method for deploying police and emergency services with the help of computers. CAD can be used to send messages to a dispatcher through a mobile data terminal (MDT) and/or it may be utilized to gather and store data; that data may consist of radio logs, field interviews, client information, or schedules. However, the great benefit of CAD is that it allows instantaneous communication between the police dispatcher and police or emergency units in the field. The dispatcher may provide call details to police officers in the field through a computer or by using a two-way radio. CAD systems have the capability of relaying text messages with call-for-service details to pagers or cell phones (via SMS or Short Message Systems).The use of CAD systems enables dispatchers to easily view and recognize the status of all field units.The displays and tools available in CAD make it possible for dispatchers to handle calls for service in highly efficient ways.

There are several CAD systems, but most—or all—provide a number of software packages that together allow for the initiation of public safety calls for service, dispatch units in the field, and follow the status of responding officers or emergency units in the field. Among the services available in a CAD program are call input, call dispatching, call status maintenance, event notes, field unit status and tracking, and call resolution and disposition. For the most part, these CAD programs are used by emergency communications dispatchers, call-takers, and 911 operators in police or emergency services call centers, as well as by field personnel able to access mobile data terminals (MDTs) or mobile data computers (MDCs).

Computer-Aided Dispatch systems usually use one or more servers located in a central dispatch office, which communicate with computer terminals in a communications center or with mobile data terminals installed in vehicles. Although there are a multitude of CAD programs that suit different department needs, the fundamentals of each system are the same. They include:

  • • Log on/off times of police personnel (sworn/non-sworn)
  • • Generating and archiving incidents that begin with a phone call from a citizen or originate from personnel in the field
  • • Assigning field personnel to incidents
  • • Updating incidents and logging those updates
  • • Generating case numbers for incidents that require an investigation
  • • Timestamping every action taken by the dispatcher at the terminal

In an ideal setting, a call is received by a call-taker and information about the call is input into the CAD template. Simply, location, reporting party, and incident are the main fields that have to be populated by type-codes. For example, if there was a burglary in progress, the type-code for that incident could be “BURG”; when BURG is typed out, then the program will spell out “BURGLARY (in progress).” If the location was at the 1400 block of Madison, the type-code could be “14MAD”The reporting party information would be populated by the call-taker including last name, first name, call-back number, etc.

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