white unit is usually located on the vertical stabilizer in a  position where it is clearly visible through a wide angle from  the rear of the aircraft.  Figure 9-176  illustrates a schematic  diagram of a position light circuit. Position lights are also  known as navigation lights. There are, of course, many variations in the position light  circuits used on different aircraft. All circuits are protected by  fuses or circuit breakers, and many circuits include flashing  and dimming equipment. Small aircraft are usually equipped  with a simplified control switch and circuitry. In some cases,  one control knob or switch is used to turn on several sets  of lights; for example, one type utilizes a control knob, the  first movement of which turns on the position lights and the  instrument panel lights. Further rotation of the control knob  increases the intensity of only the panel lights. A flasher unit  is seldom included in the position light circuitry of very light  aircraft but is used in small twin-engine aircraft. Traditional  position lights use incandescent light bulbs. LED lights have  been introduced on modern aircraft because of their good  visibility, high reliability, and low power consumption. An anticollision light system may consist of one or more  lights. They are rotating beam lights that are usually installed  on top of the fuselage or tail in such a location that the light  does not affect the vision of the crewmember or detract from  the visibility of the position lights. Large transport type  aircraft use an anticollision light on top and one on the bottom  of the aircraft.  Figure 9-177  shows a typical anticollision  light installation in a vertical stabilizer. Anticollision Lights Figure 9-176.  Navigation light system schematic. Figure 9-177.  Anticollision lights. 25-53-02 CB121 NAV LIGHT 5A W159 A223 panel assembly subpanel, L INBD WG STA 124.6 H 91-29 J282 P282 WG STA 124.6 H 91-28 J281 P281 L168D20 L168A20 L168F20 L168B20 L168G20 I P238 J238 G Ground 20 Nav light PWR 20 DS104/XDS104 R Nav light R Ground 20 Nav light PWR 20 DS104/XDS104 L Nav light C Blk Red DS103/XDS103 Tail nav light I P239 J239 L170A20N 33-47 GS129 9-102