![]() You can build an LED circuit and connect power to it, and the LED emits light. The name is usually pronounced as three letters: “L-E-D”. You will often see a light emitting diode referred to in books and circuit diagrams by the letters LED. MAKING A LIGHT EMITTING DIODE (LED) EMIT LIGHT Most of the indicator lights you see on devices are called light emitting diodes. These are usually status indicator lights that tell you what the device is up to. Other indicator lights are switched on and off by a microcontroller inside the device. In some cases, the indicator light is connected directly to the battery or power supply, like the power indicator light on the Board of Education. ![]() Turning an indicator light on and off is a simple matter of connecting and disconnecting it from a power source. Here are just a few examples of devices with indicator lights: car stereos, televisions, VCRs, disk drives, printers, and alarm system control panels. Depending on which light is on, the person using the printer knows if it is running properly or needs attention. ![]() Figure 2-1 shows three indicator lights on a laser printer. Chapter #2: Lights On – Lights Off INDICATOR LIGHTS Indicator lights are so common that most people tend not to give them much thought.
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