Emergency telephone number

In many countries the public switched telephone network has a single emergency telephone number (sometimes known as the universal emergency telephone number or the emergency services number) that allows a caller to contact local emergency services for assistance. The emergency number differs from country to country; it is typically a three-digit number so that it can be easily remembered and dialed quickly. Some countries have a different emergency number for each of the different emergency services; these often differ only by the last digit. See List of emergency telephone numbers.

The emergency telephone number is a special case in the country's telephone number plan. In the past, calls to the emergency telephone number were often routed over special dedicated circuits. Though with the advent of electronic exchanges these calls are now often mixed with ordinary telephone traffic, they still may be able to access circuits that other traffic cannot. Often the system is set up so that once a call is made to an emergency telephone number, it must be answered. Should the caller abandon the call, the line may still be held until the emergency service answers and releases the call.

An emergency telephone number call may be answered by either a telephone operator or an emergency service dispatcher. The nature of the emergency (police, fire, medical) is then determined. If the call has been answered by a telephone operator, they then connect the call to the appropriate emergency service, who then dispatches the appropriate help. In the case of multiple services being needed on a call, the most urgent need must be determined, with other services being called in as needed.

Emergency dispatchers are trained to control the call in order to provide help in an appropriate manner; they can be assisted by computer aided call handling systems (CACH). The emergency dispatcher may find it necessary to give urgent advice in life-threatening situations. Some dispatchers have special training in telling people how to perform first aid or CPR.

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