Emergency telephone number
In the past, calls to the emergency telephone number were often routed over special dedicated circuits.
In many parts of the world, an emergency service can identify the telephone number that a call has been placed from.
In small towns, operators frequently provided additional services, knowing where to reach doctors, veterinarians, law enforcement personnel and firefighters at all times.
[2] When 999 was dialed, a buzzer sounded and a red light flashed in the exchange to attract an operator's attention.
Because of the design of U.S. central office (phone) switches, it was not practical to use the British emergency number 999 (as was briefly considered).
At this point, 911 service is available in most of North America, but there are still small, sparsely-populated, or remote areas (such as Nunavut and the Northwest Territories in Canada's Arctic) that do not have it.
[10][11][12] Gradually, various problems were overcome; "smart" or "enhanced 911" systems were developed that not only would display the caller's number and address at the dispatch center but also could be configured so that 911 calls were automatically routed to the correct dispatch center, regardless of what central office the caller was served from.
As more manual telephone exchanges were converted to dial operation, more and more subscribers had access to these special numbers.
[17] 119 is an emergency telephone number in countries like for example China, Japan, South Korea and Taiwan.
In 1961, the office of the Postmaster General (PMG) introduced the Triple Zero (000) number in major population centres and near the end of the 1980s extended its coverage to nationwide.
The number Triple Zero (000) was chosen for several reasons: technically, it suited the dialing system for the most remote automatic exchanges, particularly outback Queensland.
[23] The International Telecommunication Union has officially set two standard emergency phone numbers for countries to use in the future.
AP reports that member states have agreed that either 911 or 112 should be designated as emergency phone numbers – 911 is more commonly used in the Americas, while 112 is standard across the EU and in many other countries worldwide.
[24] In January 2008, the Internet Engineering Task Force released a set of RFC documents pertaining to emergency calls in IP networks.
[26] The SIM card issued by the operator can contain additional country-specific emergency numbers that can be used even when roaming abroad.
The GSM network can also update the list of well-known emergency numbers when the phone registers to it.
[30][31] As a result, there are programs that provide donated used mobile phones to victims of domestic violence and others especially likely to need emergency services.
Since 2020, emergency responders have been able to better locate callers who dial 911 on their cellphones from indoors as the U.S. wireless industry improved caller-location for the majority of such calls.
Since mobile phones are typically carried in pockets and small bags, the keys can easily be depressed accidentally, leading to unintended calls.
[33] As earlier telephone systems used loop disconnect dialing, attention was devoted to avoiding the number being dialed accidentally by errant interruptions of the circuits by making them involve long sequences of pulses, such as with the UK 999 emergency number.
[3] This meant that "111" could not be used: "111" dialing could accidentally take place when phone lines were in too close proximity to each other.
Subscribers, as they were called then, were even given instructions on how to find the number "9" on the dial in darkened, or smoke-filled, rooms, by locating and placing the first finger in the "0" and the second in the "9", then removing the first when actually dialling.
