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Follow this link for the full explaination - How Does 9-1-1 Work
Nine-One-One (911) is the three-digit telephone number that has been designated for public use throughout the United States to report an emergency and request emergency assistance. Emergencies usually involve police, fire or emergency medical services.
The 9-1-1 system knows what phone number is calling similar to Caller ID service. However, a database is then accessed that displays much more information to the dispatcher including the address, police, fire and medical responder information and any other special notes that might be attached to the particular phone number such as special medical or physical needs.
All NON EMERGENCY PHONE CALLS should be dialed as 405-273-2121
The ultimate goal of 9-1-1 is an easy to remember and easy to use contact number for emergency purposes. 9-1-1 is NOT INTENDED for uses such as directions, questions for Police Officers or other contacts. It is ONLY INTENDED for EMERGENCY USE.