Minitor pagers have been used by volunteer fire departments and EMS agencies across the United States for decades to alert crews when a call comes in. The Minitor VI format refers to the tone and audio levels set for that pager model, and scanner recording sites such as those covering Maryland dispatch preserve these alerts from real radio traffic. This mass casualty version circulated among scanner listeners and first responder communities first, then spread to soundboards where its serious, official tone made it useful far beyond actual dispatch listening.