Transformers are devices that transform voltage. The transformers commonly used in lighting systems transform 230 V line voltage (primary side) into an extra-low voltage of 6, 12 or 24 V (secondary side). Low voltage spots and other low voltage luminaires without built-in transformer need to be operated by individual or collective upstream transformers. Magnetic transformers are conventional transformer technology. They work with different primary- and secondary-side windings. Toroidal-core transformers are frequently used. Converters for low voltage halogen lamps are smaller, more compact, lighter, quieter and more economical on electricity; they are often also called electronic transformers.