Digital clock
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A digital clock is a type of clock that uses digital electronic methods of keeping time.
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[edit] Construction
Digital clocks typically use the 50 or 60 hertz oscillation of AC power or a crystal oscillator as in a quartz movement to keep time. A digital clock typically displays a numerical hour range of 0–23, or 1–12 (with an indication of AM or PM), although digital versions of analog-style faces exist.
[edit] Displays
To represent the time, most digital clocks use a seven-segment LED, VFD, or LCD display for each of four digits. They generally also include other elements to indicate whether the time is AM or PM, whether or not an alarm is set, and so on.
[edit] Setting
One notorious drawback to digital clocks is the difficulty of setting the time in some designs. Most digital clocks flash 12:00 by default when first powered on and, since the clock is often not a critical function in many electronic devices, people often allow them to display this default.
Moreover, since they run on electricity and have no permanent memory, digital clocks must be reset every time they are moved or the power is cut off. This is a particular problem with alarm clocks, since a power outage during the night usually results in the clock failing to trigger the alarm in the morning.
To reduce the problem, later designs often incorporate a battery backup to maintain the time during power outages. More recently, some devices incorporate a method for automatically setting the time, such as using a broadcast radio time signal from an atomic clock, getting the time from an existing satellite television or computer connection, or by being set at the factory and then maintaining the time from then on with a quartz movement powered by an internal rechargeable battery.
[edit] Uses
- Digital clocks are very small, useful, and inexpensive. For these reasons, they are often incorporated into virtually every electronic device. Most commonly, digital clocks are incorporated into bedside alarm clock radios, but they are also found in televisions, microwave ovens, standard ovens, watches,computers and cell phones.
- In the 1980s and 1990s, digital clocks were standard on most automobiles. However, the fashion is slowly leaning towards analog clocks, which was the first style of clock to be used in automobiles.
[edit] History
Digital clocks were invented in 1956 and became more popular as microchips and LEDs became cheaply available.
