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Public Health - Seattle & King County

Enhanced 9-1-1 Dispatch Centers

Rapid access to the Emergency Medical Services System is an essential component of the Medic One System and vital in the Chain of Survival.

Enhanced 911 is an automated system that uses the caller's telephone number to determine their location. Citizens of Seattle and King County have benefited from the Enhanced 911 system since 1985.

This systems relies on Automatic Number Identification (ANI), normally supplied by the telephone company's end office equipment. ANI information is inserted onto a 911 call, just ahead of the caller's voice, and provided to the Enhanced 911 Dispatch Center, also known as a Public Safety Answering Point, or PSAP. At the PSAP, ANI information is routed to a database, usually at the telephone company, to retrieve Automated Location Information (ALI) data. ALI includes the caller's address and emergency response information. This all takes place in less than 3 seconds as ANI/ALI data is routed along with the voice call to a 911 Operator and is displayed on the console during the call.

When you dial 911 in Seattle and King County the following occurs:

  • Your phone number and location appear to the 911 Call Receiver on a computer screen, like the one below:
    911 phone screen

  • The Call Receiver will ask you questions about the patients condition, signs or symptoms.
  • While gathering this information, Basic Life Support (BLS) Fire Department units are dispatched.
  • If the patients condition is serious or an immediate life threat, an Advanced Life Support (ALS) Paramedic Unit is also dispatched.
  • First Aid instructions such as CPR or bleeding control are given when it is necessary.
  • The greatest service that an E911 Dispatcher provides is bridging the gap between the time you call and when help arrives. So don't be alarmed if the Call Receiver asks you to stay on the line. Help is on the way.