Emergency medical services (EMS) systems throughout the industrialized world have adopted method of predispatch screening of emergency aid calls in order that highly trained personnel on advanced life support (ALS) units are used for true emergencies and remain available for further advanced medical emergency calls. Tiered emergency medical dispatch is a system of rapid telephone assessment by trained and medically controlled emergency dispatchers who use their assessment to direct the appropriate EMS response units to the emergency situation.  The Santa Ana Fire Department Communications center is located at Fire Station #5.  Dispatchers are available to take emergency calls 24 hours a day.