Heliport lighting normally consists of a circle or square of inset lights around the surface called the TLOF (touchdown and lift-off area) and another around the overall landing area called the FATO (final approach and takeoff area). The later encompasses the TLOF as well and the lights may be elevated or inset. Both sets of lights are now recommended to be green by the International Civil Aviation Organization and Federal Aviation Administration. Yellow (amber) was the former standard and is still preferred in many locations. There is a great deal of variance in color depending on the owner and jurisdiction. These lights were traditionally incandescent but are now increasingly light-emitting diodes with brightness control. The TLOF and FATO lights may be supplemented with surface flood lights. A lighted wind cone is necessary. At ground-based locations, a row of lead-in lights in the preferred direction of approach is sometimes used. Visual slope guidance systems (such as HAPI, PAPI, etc.) are recommended in both ICAO and FAA documents but are rarely deployed due to the high cost relative to the rest of the lighting system. While airports commonly use 6.6A direct current power, heliport lighting is normally AC powered. Radio control of the lighting by the pilot via an automated ground-based controller is also common.