Arizona's rural emergency medical services communications system

In 1972, the Arizona State Legislature established the Division of Emergency Medical Services within the Arizona Department of Public Safety (DPS). As a part of the legislation, the Legislature charged the Director of the DPS with the responsibility for the establishment, operation, and maintenance of the Statewide Emergency Meidcal Services Communications System (EMSCOM). This system was to have the capability of providing for intercommunication of all law enforcement agencies and personnel, ambulances, ambulance services and dispatchers, and emergency receiving facilities and other health care institutions and medical practitioners. With financial assistance from the U.S. Department of Health, Education and Welfare, the Department of Public Safety embarked upon a demonstration program of developing an EMSCOM across the northern part of the State of Arizona. The primary aim of the program was to find the most effective means of providing two-way voice communications between the various elements of the EMS system over large geographic areas with a very sparse population located in relatively few population centers. The UHF system-designed, purchased, and installed prior to new EMS frequencies, made available by the Federal Communications Commission by their rule making in Docket #19880-presented a number of technical and operational problems related to radio signal propagation charactersitics over our large geographic areas and rugged terrain. Efforts to minimize the geographic signal propagation problems resulted in the incorporation of receiver voting-as well as associated transmitter selection-techniques. Design of the dispatch control console incorporated features to allow the console operator to communicate with all hospitals, ambulance drivers, and paramedics over the entire area of operation. The control console also incorporated the use of telephone patching equipment to allow all elements of the EMS system to communicate with each other through two-way radio, microwave, and telephone facilities.