Sometimes a fire engine or fire truck will arrive first because it is the closest emergency equipment to the scene. While waiting for the ALS unit to get to the scene, these emergency medical technicians and paramedic will render whatever aid is necessary. Along with basic medical equipment, all fire engines are equipped with automatic defibrillators, a device used to monitor the heart and deliver an electrical charge to correct a life-threatening heart rhythm. Additionally, all paramedic engines are equipped with specialized advanced life support equipment which can be used in any life-threatening emergency. Teamwork is an essential part of emergency operations, and all of the personnel on the emergency scene are trained to function as a lifesaving team.