9-1-1 ,   also written 911 , is an emergency telephone number for the North American Numbering Plan (NANP), one of eight N11 codes . Like other emergency numbers around the world, this number is intended for use in emergency circumstances only, and using it for any other purpose (such as making false or prank calls ) is a crime in certain jurisdictions.
In over 98% of locations in the United States and Canada, dialing "9-1-1" from any telephone will link the caller to an emergency dispatch office—called a public-safety answering point (PSAP) by the telecom industry—which can send emergency responders to the caller's location in an emergency. In approximately 96 percent of the U.S., the enhanced 9-1-1 system automatically pairs caller numbers with a physical address. 
In the Philippines , the 9-1-1 emergency hotline has been available to the public since August 1, 2016, although it was first available in Davao City . It is the first of its kind in Asia-Pacific region.  It replaces the previous emergency number 117 used outside Davao City.
As of 2017, a 9-1-1 system is in use in Mexico , where implementation in different states and municipalities is being conducted.
999 is used in Singapore, Malaysia, Hong Kong, the United Kingdom, and many British territories amongst other places. 112 is the equivalent emergency number used in the European Union and various other countries. In the US, some carriers, including AT&T , map the number 112 to the emergency number 9-1-1. 
In the earliest days of telephone technology, prior to the development of the rotary dial telephone , all telephone calls were operator -assisted. To place a call, the caller was required to pick up the telephone receiver , sometimes turn a magneto crank, and wait for the telephone operator to answer. The caller would then ask to be connected to the number they wished to call, and the operator would make the required connection manually, by means of a switchboard .
In an emergency, the caller might simply say "Get me the police", "I want to report a fire", or "I need an ambulance or doctor". Until dial service came into use, one could not place calls without proper operator assistance. 
The first known experiment with a national emergency telephone number occurred in the United Kingdom in 1937, using the number 999 .  In the United States, the push for the development of a nationwide American emergency telephone number came in 1957 when the National Association of Fire Chiefs recommended that a single number be used for reporting fires.  The first city in North America to use a central emergency number was the Canadian city of Winnipeg , Manitoba in 1959, which instituted the change at the urging of Stephen Juba , mayor of Winnipeg at the time.  Winnipeg initially used 999 as the emergency number,  but switched numbers when 9-1-1 was proposed by the United States. In 1967, the President's Commission on Law Enforcement and Administration of Justice recommended the creation of a single number that could be used nationwide for reporting emergencies.  The Federal Communications Commission then met with AT&T in November 1967 in order to choose the number.
In 1968, the number was agreed upon. AT&T chose the number 9-1-1, which was simple, easy to remember, dialed easily, and worked well with the phone systems in place at the time.
Just 35 days after AT&T's announcement, on February 16, 1968, the first-ever 9-1-1 call was placed by Alabama Speaker of the House Rankin Fite , from Haleyville City Hall, to U.S. Rep. Tom Bevill , at the city's police station. Bevill reportedly answered the phone with "Hello". At the City Hall with Fite was Haleyville mayor James Whitt; at the police station with Bevill were Gallagher and Alabama Public Service Commission director Eugene "Bull" Connor . Robert Fitzgerald, Inside State Plant Manager for the Alabama Telephone Company, was at the ATC central office serving Haleyville and actually observed the call pass through the switching gear as the mechanical equipment clunked out "9-1-1". The phone used to answer the first 9-1-1 call, a bright red model, is now in a museum in Haleyville, while a duplicate phone is still in use at the police station .
In 1968, 9-1-1 became the national emergency number for the United States. Calling this single number provided a caller access to police, fire, and ambulance services, through what would become known as a common public-safety answering point (PSAP). The number itself, however, did not become widely known until the 1970s, and many municipalities did not have 9-1-1 service until well into the 1980s. For example, although the City of Chicago, Illinois , had access to 9-1-1 service as early as 1976, the Illinois Commerce Commission did not authorize telephone service provider Illinois Bell to offer 9-1-1 to the Chicago suburbs until 1981.  Implementation was not immediate even then; by 1984, only eight Chicago suburbs in Cook County had 9-1-1 service.  As late as 1989, at least 28 Chicago suburbs still lacked 9-1-1 service; some of those towns had previously elected to decline 9-1-1 service due to costs and—according to emergency response personnel—failure to recognize the benefits of the 9-1-1 system. 
Conversion to 9-1-1 in Canada began in 1972, and now virtually all areas, except for some rural areas, are using 9-1-1. As of 2008, each year Canadians make twelve million calls to 9-1-1.
On September 15, 2010, AT&T announced that the State of Tennessee had approved a service to support a text to 9-1-1 trial statewide, where AT&T would be able to allow its users to send text messages to 9-1-1 public-safety answering points (PSAPs). 
In all North American jurisdictions, special privacy legislation permits emergency operators to obtain a 9-1-1 caller's telephone number and location information.  This information is gathered by mapping the calling phone number to an address in a database. This database function is known as Automatic Location Identification (ALI).  The database is generally maintained by the local telephone company, under a contract with the PSAP. Each telephone company has its own standards for the formatting of the database. Most ALI databases have a companion database known as the MSAG, Master Street Address Guide. The MSAG describes address elements including the exact spellings of street names, and street number ranges.
In the case of mobile phones , the associated billing address is not necessarily the location to which emergency responders should be sent, since the device is portable. This means that locating the caller is more complicated, and there is a different set of legal and technical requirements. To locate a mobile telephone geographically, there are two general approaches: to use some form of radiolocation from the cellular network , or to use a Global Positioning System receiver built into the phone itself. Both approaches are described by the radio resource location services protocol (LCS protocol). Depending on the mobile phone hardware, one of two types of location information can be provided to the operator. The first is Wireless Phase One (WPH1), which is the tower location and the direction the call came from, and the second is Wireless Phase Two (WPH2), which provides an estimated GPS location.
As Voice over Internet Protocol (VoIP) technology matured, service providers began to interconnect VoIP with the public switched telephone network and marketed the VoIP service as a cheap replacement phone service. However, E911 regulations and legal penalties have severely hampered the more widespread adoption of VoIP: VoIP is much more flexible than land line phone service, and there is no easy way to verify the physical location of a caller on a nomadic VoIP network at any given time (especially in the case of wireless networks), and so many providers offered services which specifically excluded 9-1-1 service so as to avoid the severe E-911 non-compliance penalties. VoIP services tried to improvise, such as routing 9-1-1 calls to the administrative phone number of the Public Safety Answering Point, adding on software to track phone locations, etc.
In response to the E911 challenges inherent to IP phone systems, specialized technology has been developed to locate callers in the event of an emergency. Some of these new technologies allow the caller to be located down to the specific office on a particular floor of a building. These solutions support a wide range of organizations with IP telephony networks. The solutions are available for service providers offering hosted IP PBX and residential VoIP services. This increasingly important segment in IP phone technology includes E911 call routing services and automated phone tracking appliances. Many of these solutions have been established according to FCC, CRTC, and NENA i2 standards, in order to help enterprises and service providers reduce liability concerns and meet E911 regulations. 
9-1-1 dispatchers use computer-aided dispatch (CAD) to record a log of police, fire, and EMS services. It can either be used to send messages to the dispatchee via a mobile data terminal (MDT) and/or used to store and retrieve data (i.e. radio logs, field interviews, client information, schedules, etc.). A dispatcher may announce the call details to field units over a two-way radio. Some systems communicate using a two-way radio system's selective calling features.
CAD systems may send text messages with call-for-service details to alphanumeric pagers or wireless telephony text services like SMS. The central idea is that persons in a dispatch center are able to easily view and understand the status of all units being dispatched. CAD provides displays and tools so that the dispatcher has an opportunity to handle calls-for-service as efficiently as possible.
Funding 9-1-1 services
In the United States, 9-1-1 and enhanced 9-1-1 are typically funded based on state laws that impose monthly fees on local and wireless telephone customers. In Canada, a similar fee for service structure is regulated by the federal Canadian Radio Television and Telecommunications Commission (CRTC).
Depending on the location, counties and cities may also levy a fee, which may be in addition to, or in lieu of, the federal fee. The fees are collected by local telephone and wireless carriers through monthly surcharges on customer telephone bills. The collected fees are remitted to 9-1-1 administrative bodies, which may be statewide 9-1-1 boards, state public utility commissions, state revenue departments, or local 9-1-1 agencies.  These agencies disburse the funds to the Public Safety Answering Points for 9-1-1 purposes as specified in the various statutes.
Telephone companies in both the United States and Canada, including wireless carriers, may be entitled to apply for and receive reimbursements for costs of their compliance with federal and state laws requiring that their networks be compatible with 9-1-1 and enhanced 9-1-1.
Fees vary widely by locality. They may range from around $.25 per month to $3.00 per month, per line.  The average wireless 9-1-1 fee in the United States , based on the fees for each state as published by the National Emergency Number Association (NENA), is around $.72.
Monthly fees usually do not vary based on the customer's usage of the network, though some states do cap the number of lines subject to the fee for large multi-line businesses.
Emergency service response
Reaching a 9-1-1 dispatcher does not guarantee that emergency services will actually be able to respond to the call, as they are funded and operated separately. One egregious example occurred during a budget crunch in Josephine County, Oregon in 2013, when no county police were on duty and no state police were available to respond to a female caller whose abusive ex-boyfriend was in the process of breaking into her apartment. After the caller spent ten minutes on the phone with the dispatcher, the ex-boyfriend succeeded in breaking in and raping her. 
In 2013, the next-of-kin of Detroit murder victim Stacey Hightower sued the city for its 90-minute 9-1-1 response time.  For Robert Poff, a patient experiencing problems breathing, a twenty-minute delay in summoning emergency medical aid proved fatal.  Police emergency response times in the bankrupt city in 2013 were typically fifty minutes  to one hour,  and ambulance response times at least twelve to twenty minutes. 
Problems with 9-1-1
In the U.S., some states have rules requiring that every landline telephone that can access the network be able to dial 9-1-1, regardless of any reason that normal service may have been disconnected (including non- payment ). (This only applies to states with a Do Not Disconnect policy in place.) Telephone companies in those states must provide a "soft" or "warm" dial tone service; details can be found at FCC .  On wired ( land line ) phones, this usually is accomplished by a "soft" dial tone , which sounds normal but will allow only emergency calls. Often, an unused and unpublished phone number will be issued to the line so that it will work properly.
With regard to mobile phones, the rules require carriers to connect 9-1-1 calls from any mobile phone, regardless of whether that phone is currently active.  Similar rules for inactive telephones apply in Canada. 
When a cellular phone is deactivated, the phone number is often recycled to a new user, or to a new phone for the same user. The deactivated cell phone will still complete a 9-1-1 call (if it has battery power) but the 9-1-1 operator will see a specialized number indicating the cell phone has been deactivated. It is usually represented with an area code of (911)-xxx-xxxx. If the call is disconnected, the 9-1-1 operator will not be able to connect to the original caller. Also because the cell phone is no longer activated, the 9-1-1 operator is often unable to get Phase II information . 
About 70 percent of 9-1-1 calls came from cell phones in 2014,  and finding out where the calls came from required triangulation . A USA Today study showed that where information was compiled on the subject, many of the calls from cell phones did not include information allowing the caller to be located. Chances of getting as close as 100 feet were higher in areas with more towers. But if a call was made from a large building, even that would not be enough to precisely locate the caller. New federal rules, which service providers helped with, require location information for 40 percent of calls by 2017 and 80 percent by 2021. 
As recently as 21 April 2016, an unidentified caller dialing 9-1-1 to report the death of the musical artist Prince still needed to provide the 9-1-1 dispatcher with the physical address of the building in which the musician had died because the dispatcher had no other means to determine the location of the caller's cell phone. The caller was asked to locate a piece of mail with the building's address so that emergency responders could be sent. 
If 9-1-1 is dialed from a commercial Voice over Internet Protocol ( VoIP ) service, depending on how the provider handles such calls, the call may not go anywhere at all, or it may go to a non-emergency number at the public safety answering point associated with the billing or service address of the caller.  Because a VoIP adapter can be plugged into any broadband internet connection, a caller could actually be hundreds or even thousands of miles away from home, yet if the call goes to an answering point at all, it would be the one associated with the caller's address and not the actual location of the call. It may never be possible to reliably and accurately identify the location of a VoIP user, even if a GPS receiver is installed in the VoIP adapter, since such phones are normally used indoors, and thus may be unable to get a signal.
In March 2005, commercial Internet telephony provider Vonage was sued by the Texas Attorney General , who alleged that their website and other sales and service documentation did not make clear enough that Vonage's provision of 9-1-1 service was not done in the traditional manner. In May 2005, the FCC issued an order requiring VoIP providers to offer 9-1-1 service to all their subscribers within 120 days of the order being published.  The order set off anxiety among many VoIP providers, who felt it will be too expensive and require them to adopt solutions that won't support future VoIP products. In Canada, the federal regulators have required Internet service providers (ISPs) to provide an equivalent service to the conventional PSAPs, but even these encounter problems with caller location, since their databases rely on company billing addresses. 
In May 2010, most VoIP users who dial 9-1-1 are connected to a call center owned by their telephone company, or contracted by them. The operators are most often not trained emergency service providers, and are only there to do their best to connect the caller to the appropriate emergency service. If the call center is able to determine the location of the emergency they try to transfer the caller to the appropriate PSAP. Most often the caller ends up being directed to a PSAP in the general area of the emergency. A 9-1-1 operator at that PSAP must then determine the location of the emergency, and either send help directly, or transfer the caller to the appropriate emergency service.
VoIP services operating in Canada are required to provide 9-1-1 emergency service.  In April 2008, an 18-month-old boy in Calgary, Alberta died after a Toronto VoIP provider's 9-1-1 operator had an ambulance dispatched to the address of the family's previous abode in Mississauga, Ontario . 
The U.S. Federal Bureau of Investigation has warned of an increase in deliberate false alarms in which a false origin is displayed on calls to emergency services to send SWAT teams or heavily armed police to unsuspecting citizens' doorsteps.  Voice over IP (VoIP) has contributed greatly to the problem by making call origin more difficult to determine quickly and reliably.
Emergencies across jurisdictions
When a caller dials 9-1-1, the call is routed to the local public safety answering point. However, if the caller is reporting an emergency in another jurisdiction, the dispatchers may or may not know how to contact the proper authorities. The publicly posted phone numbers for most police departments in the U.S. are non-emergency numbers that often specifically instruct callers to dial 9-1-1 in case of emergency, which does not resolve the issue for callers outside of the jurisdiction. In the age of both commercial and personal high speed Internet communications, this issue is becoming an increasing problem.
NENA has developed the North American 9-1-1 Resource Database which includes the National PSAP Registry. PSAPs can query this database to obtain emergency contact information of a PSAP in another county or state when it receives a call involving another jurisdiction. Online access to this database is provided at no charge for authorized local and state 9-1-1 authorities. 
In the 919 area code , including Raleigh, North Carolina and surrounding communities, a second area code (984) was added using an overlay plan in 2011. Starting in March 2012, people making calls from the 919 area code had to dial the entire number including area code even for local calls, and many people started with 9-1-1, realized their mistake, and disconnected. Three months after the change, police in Wake County were responding to six times as many "hang-ups", all of which required a response. This response could be a call-back from the dispatcher (slowing down the ability to respond to actual emergencies), or if that did not get a result, a visit from the police. A supervisor recommended that people remain on the line and explain the mistake.   For all of 2012, the number of hang-ups in Wake County was nearly three times what it had been before the switch; over 30,000 police responses resulted.  In 2014, hang-up calls remained high, at about four times the rate from before. 
PBX systems requiring a "9" to reach an outside line and a "1" used to indicate an area code can be a problem. If the telephone buttons don't take input correctly or the caller accidentally presses a button multiple times, the caller might misdial 9-9-1-1 (rather than 9-1). If so, the first 9 connects to the outside network, and then a 9-1-1 call is placed.
Making calls public
News programs and such shows as Rescue 911 have broadcast actual calls to 9-1-1 centers.
Ohio Senator Tom Patton introduced a bill in 2009 which would have banned the broadcasting of 9-1-1 calls, requiring the use of transcripts instead. Patton believed that people would be reluctant to make calls because of possible retaliation or threats against those who called. He intended to seek proof of this idea to satisfy those who did not believe him, or that broadcasting 9-1-1 calls hurt investigations. The Ohio Fraternal Order of Police supported the bill because broadcasts of 9-1-1 calls have been " sensationalized ".  Ohio Association of Broadcasters director Chris Merritt said the government should not have the right to decide how public records were used.  Other opponents of such a ban point out that recordings hold dispatchers accountable and show when they are not doing their jobs properly, in a way transcripts cannot.  
A bill signed by Alabama governor Bob Riley on April 27, 2010, requires a court order before recordings can be made public. Alaska , Florida , Kentucky , and Wisconsin also had bills banning the broadcasts.  Mississippi , Missouri , Pennsylvania , Rhode Island , and Wyoming already banned the broadcasts.