Digital clocks display the time electronically.
Definition
A digital clock is technically only a clock that displays the time in a digital fashion instead of an analog fashion. That means that instead of using hands that circle around a face of a clock, the numbers are displayed using simple lighting technology. There are analog clocks that use electronic systems to control the hands, but far fewer digital clocks that use analog systems--in almost all cases, digital clocks use electronic components that accomplish the same tasks.
Display
When a digital clock is being manufactured, one of the most important parts is the face plating of the clock itself, which shows the numbers. These small faces are either made of LED or LCD. LCD, or liquid crystal displays, use crystals suspended in a fluid solution that can refract light in specific ways to create different colors (usually just one color, in a digital clock). The display itself can either be a complex dot-matrix arrangement that allows for more detailed numbers and pictures, or a seven-segment display, which is a composition of seven LCD bars that can be turned on or off in different segments to create a number 1 through 9. LED clocks use light-emitting diodes that radiate light instead of simply refracting it, leading to brighter displays and a much wider range of colors.
Other components
Once the display plate is made, it is combined with the other components, including the battery or charging system. A digital clock needs access to a continual source of power, so it is equipped with either a simple battery or battery compartment, or an AC adapter that can be plugged in to receive power from the household. If a digital clock is designed to be plugged into the wall, it can use the 60-Hz oscillations present in AC power to measure time using a digital counter that measures each hertz as it passes by to figure out the seconds. Digital clocks without adapters use a crystal oscillator (a crystal subjected to a current) that is more accurate.
To control the power flow to the display, different types of gating circuits are installed to direct the current to different segments of the clock, as directed by the counter. Other necessary types of electronic devices are also installed, including a bridge rectifier, a volt regulator, capacitors and resistors to manage the flow of the current.
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