Written By: Ehsan Jahandarpour

A public-safety answering point (PSAP), sometimes called “public-safety access point”, is a call center responsible for answering calls to an emergency telephone number for police, firefighting, and ambulance services. Trained telephone operators are also usually responsible for dispatching these emergency services. Most PSAPs are now capable of caller location for landline calls, and many can handle mobile phone locations as well (sometimes referred to as phase II location), where the mobile phone company has a handset location system. Some can also use voice broadcasting, where outgoing voice mail can be sent to many phone numbers at once, in order to alert people to a local emergency such as a chemical spill. In the United States, the county or a large city usually handles this responsibility. As a division of a U.S. state, counties are generally bound to provide this and other emergency services even within the municipalities, unless the municipality chooses to opt out and have its own system, sometimes along with a neighboring jurisdiction. If a city operates its own PSAP, but not its own particular emergency service (for example, city police but county fire), it may be necessary to relay the call to the PSAP that does handle that type of call. The U.S. requires caller location capability on the part of all phone companies, including mobile ones, but there is no federal law requiring PSAPs to be able to receive such information. There are roughly 6100 primary and secondary PSAPs in the U.S. Personnel working for PSAPs can become voting members of the National Emergency Number Association (NENA). Emergency dispatchers working in PSAPs can become certified with the National Academies of Emergency Dispatch (NAED), and a PSAP can become an NAED Accredited Center of Excellence. Each PSAP has a ‘real’ telephone number that is called when the emergency number (911) is dialed. The telecommunications operator is responsible for associating all landline numbers with the most applicable (often the nearest) PSAP, so that when emergency number is dialed, the call is automatically routed to the most suitable PSAP. PSAP’s can be subject to changes including new contact information and changing coverage area. Commercial products exist that purport to keep pace with these changes and allow the telecommunications operator to associate numbers with the relevant PSAP based upon their physical address associated with that number. In other countries, this is the responsibility of other types of local government, and the particular setup of the telephone network dictates how such calls are handled. There is also now the ability to answer text messages at some PSAPs, which is useful in areas where weak signal strength due to distance from the nearest cell site causes fringe reception, resulting in blocked or dropped calls. Since SMS messages only require an instant to send, a brief peak in radio propagation (such as due to changing cloud cover) is often enough to get a message sent. Text messages are also useful for the deaf, as it does not require a TTY device.