Emergency 9-1-1 service was first implemented in the City of Los Angeles on October 1, 1984.
Also see: L.A. Video: Ask a Dispatcher - California Highway Patrol
The 911 emergency telephone system is in place to assist citizens with POLICE, MEDICAL or FIRE emergencies. It should be realized that non-emergency calls to the 911 system can create delays in handling other very serious emergencies that require immediate attention.
Don't assume that the 911 center answering a call from your cell phone will be the agency closest to you. Triangulation (pinpointing a cell call by the nearest local cell tower) is relatively new and only a few locales have this technology in place. Therefore, most emergency calls from cell phones are routed to a central communications center. There, the nature and location of the incident is ascertained and the 911 caller is either transferred to the appropriate agency or the gathered data is disseminated to the agency needing to respond. When you dial 911 from a cell phone, don't blurt out a street address and then expect that the 911 operator will know which town or city you are in. Chances are they cover a wide area and will need to know your exact location. They will then transfer you to the communications center best suited to help you.
The following are guidelines for the proper use of the 911 system for FIRE and MEDICAL emergencies.
These are general guidelines - If there is any doubt, do not hesitate to call for help.
911 should only be used when a true emergency exists, "POLICE", "FIRE", or "MEDICAL". Identify your call as a MEDICAL or FIRE emergency and it will be automatically transferred to the appropriate dispatch center . The dispatcher will ELECTRONICALLY RECEIVE the address and telephone number OF THE CALLER. However, if you are calling for someone else at a different location, be sure to make that known to the dispatcher.
The accuracy of all telephone numbers and addresses must be verified again by the dispatcher.
DO NOT HANG UP until the 911 dispatcher tells you to do so.
Remain calm and give direct answers to the questions asked. Speak slowly and clearly. You will be asked additional questions so the dispatcher can send the right type of help. All questions are important, even if repetitive.
The dispatcher may also provide you with CRITICAL PRE-ARRIVAL INSTRUCTIONS, such as CPR (Cardio-Pulmonary Resuscitation) or the Heimlich Maneuver.
Understanding what happens when a 911 call is placed will help the system run more efficiently and will bring you the emergency medical service you need in the shortest possible time.
Above information from the Los Angeles Police Department and Los Angeles County Sheriff's Department.