The ATS4000VA-230/110V U is a type of toroidy transformer, which is a type of electrical transformer that uses a ring-shaped core made from a ferromagnetic material around which wire is wound. This transformer is rated at 4000VA, or Volt-Amps, and operates at both 230V and 110V hook-up configurations. It is constructed with heavy duty windings, low losses, compact design, and low electromagnetic interference output. This toroidy transformer is often used in industrial, commercial, and residential applications.