9-1-1

In most parts of the United States and Canada, dialing 9-1-1 on any phone will connect the caller directly to comprehensive emergency services that includes police, the fire department and ambulance services. Slowly introduced into most major urban areas starting in the late 1970s, it now exists in almost all urban areas and is only absent in very remote areas such as the Canadian Arctic. The 9-1-1 system replaces operator-assisted emergency services where the call was routed to the appropriate emergency service, and specialized local numbers for each of the three emergency services. 
Because of the design of 9-1-1 systems, operators will immediately be informed of the phone number where the call originates, even if it would normally be blocked. The address of the caller will also appear immediately Many systems are capable of accessing the GPS information from mobile phones. 
the 9-1-1 operator is also directly connected to all emergency services and can dispatch a call directly from a computer console without having to repeat information to other emergency services - the information is all transferred automatically. Operators go through a protocol to ensure that assistance arrives as soon as possible. For example, because most people live closer to a fire station than an ambulance station, the dispatcher will send a fire truck to a medical emergency because it is equipped with first aid and trained personnel. They will stabilize and protect the patient until an ambulance arrives. In a situation where a danger is posed to a patient, the dispatcher can send police as an escort for the ambulance personnel as well. 
9-1-1 at Wikipedia