Lighting System Lamps

     Headlamps

    A headlamp is a lamp，usually attached to the front of a vehicle，with the purpose of illuminating the road ahead during periods of low visibility, such as night or precipitation.A headlamp system is required to produce a low and a high beam, which may be achievedeither by an individual lamp for each function or by a single multifunction lamp. Highbeams cast most of their light straight ahead，maximizing seeing distance, but producingtoo much glare for safe use when other vehicles are present on the road. Low beams havestricter control of upward light to provide safe forward visibility without excessive glare.They are characterized by a distinct horizontal "cutoff" line at the top of the beam. Belowthe line is bright, and above is dark. On the side of the beam facing away from oncomingtraffic, this cutoff sweeps or steps upward to direct light to road signs and pedestrians.

    The headlight switch

    The headlight switch operates the exterior and interior lights of most vehicles. The headlight switch is connected directly to the battery through a fusible link and hascontinuous power or is "hot" all the time. A circuit breaker is built into most headlightswitches to protect the headlight circuit. The interior dash lights can be dimmed manuallyby rotating the headlight switch knob，which controls a variable resistor built into theheadlight switch. The rheostat drops the voltage sent to the dash lights.

    Dimmer switches

    The headlight switch controls the power or hot side of the headlight circuit. Thecurrent is then sent to the dimmer switch，which allows current to flow to either the high-beam or the low-beam filament of the headlight bulb. An indicator on the dash whenever the bright light illuminates is selected.

    Foglamps

    Foglamps provide a wide, bar-shaped beam of light with a sharp cutoff at the top，andare generally aimed and mounted low. They may be either white or selective yellow. Theyare intended for use at low speed to increase the illumination directed towards the roadsurface and verges in conditions of poor visibility due to rain，fog，dust or snow.

    Parking lamps (Front position lamps)

    Nighttime standing-vehicle conspicuity to the front is provided by front positionlamps，known as parking lamps or parking lights. The front position lamps may emitwhite or amber light. With the vehicle's ignition switched off, the operator may activatelow-intensity lights at the front and rear on both the left and the right sides of the car.This function is used when parking in narrow unlit streets to provide parked-vehicleconspicuity to approaching drivers.

    Tail lamps (Rear position lamps)

    Nighttime vehicle conspicuity to the rear is provided by two rear position lamps (taillamp，taillight or rear light). They are required to produce only red light，and to be wiredsuch that they are lit whenever the front position lamps are illuminated，including whenthe headlamps are on. Rear position lamps may be combined with the vehicles brakelamps, or. separate from them.  In combined-function installations，the lamps producebrighter red light for the brake lamp function, and dimmer red light for the rear positionlamp function.

    Rear registration plate lamp

    The rear registration plate must be illuminated by a white lamp whenever the positionlamps are active.

    Turn signals

    Turn signals are signal lights mounted near the left and right front and rear corners，and sometimes on the sides of vehicles，used to indicate to other drivers that the operatorintends a lateral change of position (turn or lane change).

    Turn signals are required to blink on and off, or "flash"，at a steady rate of between60 and 120 blinkWer minute. Worldwide regulations stipulate an audiovisual telltale whenthe turn signals are activated; this usually takes the form of one combined or separate leftand right green indicator lights on the vehicle's instrument panel，and a cyclical "ticktack"noise generated electromechanically or electronically.

    Stop lamps (brake lights)

    Red-colored steady-burning rear lights, brighter than the tail lamps，are activatedwhen the driver applies the vehicle's brakes. These are called brake lights or stop lamps.They are required to be fitted in multiples of two，symmetrically at the left and right edgesof the rear of every vehicle.

    Brake lights use the high-intensity filament of a double-filament bulb. The lowerintensity filament is for the tail-lights. The brake light switch is a normally open(N. O.）switch but is closed when the driver depresses the brake pedal.

    Reversing lamps

    To provide illumination to the rear when backing up，and to warn adjacent vehicleoperators and pedestrians of a vehicle's rearward motion, each vehicle must be equippedwith at least one rear-mounted，rear-facing reversing lamp. These are currently required toproduce white light.

    Side turn signals

    In most countries，cars must be equipped with side-mounted turn signal repeaters tomake the turn indication visible laterally rather than just to the front and rear of thevehicle.

    Courtesy lights

    Courtesy light is a generic term primarily used for interior lights，including overhead(dome) and under-the-dash lights. These interior lights can be operated by rotating theheadlight switch knob fully counterclockwise or by operating switches located in the doorjambs.