The lighting system in a typical automobile includes the headlight, parking lights, direction-signal lights, side marker, stoplights, backup lights, tail lights, and interior lights.

Main Lighting Switch

The main lighting switch (sometimes called the headlight switch) is the heart of the lighting system. It cintrols the headlights, parking lights, side marker lights, taillights, license plate light, instrument panel lights, and imterior lights.

Individual switches are provided for special purpose lights such as directional signals, hazard warning flashers, back up lights, and courtesy lights. The main lighting switch may be of either the “push-pull”or “push-pull with rotary contact” types. A typical switch will have three positions: off, parking, and headlamps. Some switches also contain a rheostat to control the brightness of the instrument panel lights. The rheostat is operated by rotating the control knob, separating it from the push-pull action of the main lighting switch.

When the main lighting switch completes the circuit to the headlamps, the low beam lights the way for city driving and for use when meeting oncoming traffic on the highway. When the dimmer switch is actuated, the single filament headlamps go “on”, along with the high beam of the two filament headlamps. The next actuation of the dimmer switch returns the headlight system to low bearms only on the two filament lamps. Some cars are equipped with an electronic headlight dimming device, which automatically switches the headlights from high beam to low in response to light from an approaching wehicle or light from the taillight of a vehicle being overtaken. The dimmer switch in the automatic headlamp dimming system is a special override type. It is located in the steering column as part of a combination dimmer, horn, and turn signal switch. The override action occurs when a slight pull toward the driver on the switch lever provides high beam headlights regardless of the amount of light on the sensor-amplifier.

For some years there has been discussion about the advantages of a polarized healight system. Such a system comprises headlights which produce polarized light in a particular plane. The windscreens of all cars would be fitted with polarizing glass, which would be oriented so that glare from an approaching vehicle would be essentially eliminated, while the forward vision would still be kept at the present levels. The advantages the system appear attractive, but the practical problems of making the transition are very great, since it would not be practical to convert all existing vehicles to this type of lighting. Also, any benefits would only be marginal because glare itself is not a frequent cause of accidents. However, many cars now have refracting or colored glass to cut down on glare.

Directional Signal Switch

The directional signal switch is installed just below the hub of the steering wheel. A manually controlled lever projecting from the swich permits the driver to signal the direction in which he wants to turn. Moving the switch handle down will light the “turn signal” lamps on the left front and left rear of the car, signaling a left turn. Moving the switch upward will light the turn signal lamps on the right (front and rear), signaling a right turn. With the switch in a position to signal a turn, lights are alternately turned “on” and “off” by a turn signal flasher. Incorporated in the directional signal switch is a “lane change switch mechanism”.This featuue provides the driver the opportunity to signal a lane change by holding the turn lever against a detent, then releasing it to cancel the signal immediately after the maneuver is completed.

Stoplight Switch

In order to signal a stop, a brake pedal operated “stoplight switch” is provided to operate the vehicle’s stop lamps. In addition to lighting the conventional rear lights, the switch also operates the center hight-mounted stop lamp, which became mandatory on later models. Cruise control equipped vehicles may also utilize a vacuum release valve. In this case, both the vacuum release valve and the stoplight switch are actuated by movement of the brake pedal.

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普通车的照明系统包括前照灯、泊车灯、转向信号灯、轮廓灯、制动灯、倒车灯、尾灯及车内灯。

灯光总开关

灯光总开关是照明系统的心脏。它控制前照灯、泊车灯、轮廓灯、尾灯、牌照灯、仪表板灯和车内灯。

个别的开关被提供作为控制特别的灯，像是转向信号、危险警告闪烁装置、倒车灯和礼貌灯。灯光总开关可能是“拉杆式的”或“拉杆及扭旋式”类型。一个典型的开关一般有三个位置：关闭、泊车和前照灯。一些开关也包含一个可变电阻器，控制仪表板灯的灯光亮度。可变电阻器由旋转地控制手柄操纵，与灯光总开关的唯一拉的操作是分开的。

当灯光总开关接通前照灯线路的时候，近光灯丝点亮，为在城市道路驾驶和在高速公路上两车交会时提供照明。当变光开关工作时， 单丝前照灯打开，同时双丝前照灯的远光灯也一起打开。变光开关的另一个接通时，双丝前照灯上只有近光灯打开。一些汽车装备了前照灯电子变光装置，当接收到一辆逐渐靠近的汽车的灯光时，或接收到前面被赶上的车的尾灯灯光时，能自动地将前照灯从远光转变到近光。自动前照灯的变光开关是一种特别的开关。它位于转向柱上，作为组合变光开关、喇叭和转向信号开关的一部分。轻轻朝着驾驶员的方向拉动开关控制杆这一动作，就可以使前照灯远光灯泡点亮，而不用顾及灯的数量。

近年来，人们开始讨论有关偏振光的前照灯系统的优势。一个这样的系统包括能产生偏振光的特殊面的前照灯。所有的汽车挡风玻璃会配备有偏振光玻璃，这样，来自某一正在接近的汽车的眩目的光线会被定向除去，于是向前的视角就能够保持当前的水平方向。该系统的优势显得很有吸引力，但是实际的制造上的问题非常大，因为将现存汽车全部改换成这种系统显然不实际。这些益处只是次要的，因为眩目本身并不是意外事件发生的常见因素。因此，许多汽车现在装备使光线折射的玻璃或把玻璃染色来减少眩目的影响。

转向开关

转向开关就安装在转向柱毂的下面。从开关上突出的一个用手控制的杠杆使驾驶员能根据所转的方向显示转向信号。向下移动开关柄将会点亮车辆左前和左后的“转向信号灯”，表示向左转。向上移动开关将会点亮车辆右边（前面和后面）的灯，表示向右转。藉由一个转向开关表示方向信号，转向灯被一个转向信号闪光器和交替地控制“ON”和“OFF”。合并在转向开关中的是一个“变速开关机构”。该特征提供给驾驶员一个机会来握住转向杆，靠向一个爪来表示一个变换信号，在操纵完之后，释放它就可以立刻取消该信号。

制动灯开关

为了要表示停车，由刹车踏板操纵“制动灯开关”控制汽车的制动灯。除了传统照明的后灯，开关也控制中央高位刹车灯，在最新的车型中是强制性安装的。装备了巡航控制的汽车也可能利用一个真空释放阀。在这种情况下，真空释放阀和制动灯开关都由刹车踏板的运动控制。