Emergency Telephone Number - Configuration and Operation

Configuration and Operation

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.

In many parts of the world, an emergency service can identify the telephone number that a call has been placed from. This is normally done using the system that the telephone company uses to bill calls, making the number visible even for users who have unlisted numbers or who block caller ID. For an individual fixed landline telephone, the caller's number can often be associated with the caller's address and therefore their location. However, with mobile phones and business telephones, the address may be a mailing address rather than the caller's location. The latest "enhanced" systems, such as Enhanced 911, are able to provide the physical location of mobile telephones. This is often specifically mandated in a country's legislation.