from when a person calls for assistance to the time assistance arrives. The American Heart Association recommends early defibrillation to be beneficial to an individual suffering cardiac arrest and as such most fire apparatus carry automated external defibrillators (AEDs) with trained EMTs to begin stabilizing the patient prior to EMS arrival. Each fire department or fire district is independent and as such have varying response guidelines. Some agencies respond to only the most serious calls while others will respond on nearly every call. Other ambulance services Several other ambulance services exist within Louisville-Jefferson County such as Anchorage EMS. Anchorage EMS is an ambulance taxing district (as well as a fire protection taxing district) that serves the City of Anchorage as well as eastern Jefferson County with advanced life support services. Other, private ambulance agencies such as Rural/Metro Corporation and Yellow EMS provide services for parts of areas near by or within Jefferson County. For example, the City of Jeffersontown in southeastern Jefferson County has for years outsourced its EMS needs. Currently a contract exists with Yellow EMS (YEMS) to provide emergency medical services within the Jeffersontown city limits. YEMS also provides additional assistance during extremely high call volume times to LMEMS and responds to many of LMEMS' low-priority calls. Although these jurisdictions maintain their own ambulance providers, Louisville-Jefferson County government is ultimately responsible for ensuring emergency care is available and in the case that any of these providers cannot operate, LMEMS will ensure a response. LMEMS also provides mutual aid to other agencies as well. LMEMS paramedics are often called upon to provide assistance to BLS ambulance crews from other services and other counties when their own advanced providers are unavailable. Specialized teams In addition to the primary task of providing emergency care and transportation, LMEMS also maintains employees assigned to provide specialized service such as Tactical Medics to the Louisville Metro Police Department (LMPD) Special Weapons and Tactics Team (SWAT), Dive Medics and Swift-Water Rescue Medics, as well as retaining a highly visible bicycle team. Personnel are also assigned to the federally administered Joint Emergency Service Unit which seeks to combine all aspects of public safety in a large area into one task force to better coordinate activities in the event of a major emergency. Deployment Ambulances may be staffed by two Emergency Medical Technicians, one Emergency Medical Technician and one paramedic or, rarely, two paramedics. There is also