In the U.S., call firefighters respond as needed on a part-time basis to all types of emergencies. Call firefighters train with their local engine companies in their districts. Call firefighters are utilized in three different ways. “First Responder" call firefighter units, are those units that are staffed entirely by paid call firefighters. These firefighters respond to all emergency incidents within their jurisdictional areas and are supported by full-time companies from adjoining jurisdictions. "Supplemental" call firefighter units are those units that staff a second engine company from a station that is also staffed by a full-time company. These units respond to all multi-unit responses in their district, and cover the station when the career companies are committed. "Augmentation" call firefighters are assigned to an existing career company and respond directly to the scene to augment that company's staffing.