Alarm clocks have awakened us ever since they were first patented in 1847. Today, modern alarm clocks have digital components that replace mainsprings with batteries and swap clockwork for circuit boards. Though designs for digital alarm clocks vary, several common features can be found on nearly all of the models now sold.
Display
Digital clocks usually have a common LED or LCD screen. The display will show the time and indicate whether it is a.m. or p.m. Other indicators will show when the alarm is activated and whether it is set to buzz, beep or use an alternative audio source such as a radio. Some will also display the date.
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Buttons and Switches
Though the specific button configuration will vary from one model to the next, most alarm clocks provide some of the following.
The snooze button is a larger button, often centrally located. Pressing this button when the alarm is sounding will silence it, but only for a brief period.
Clock-setting controls will usually have two or more buttons, allowing the user to change the time or the alarm by cycling through hours and minutes. These buttons frequently use up and down arrows to tell which direction the time will cycle when pressed.
Clocks with a built-in radio will also include digital or analog controls that allow the user to change the station, change the volume and switch between AM and FM bands. These clock/radio models will also offer a switch or button that allows the user to toggle between the standard alarm or radio broadcast when the alarm is activated.
Power Source
Like all electric devices, digital alarm clocks require electricity to operate. Several models plug into a standard wall socket while others run on battery power.
Many alarm clocks use both, relying on the outlet power for normal use but turning to the battery as a backup power supply when there is a blackout or when the unit is unplugged. Units without such a backup are prone to resetting completely when power is disrupted. As a result, a late-night power outage can prevent the alarm from working the next morning.
Internal Circuitry
Unlike mechanical alarm clocks, which relied on a carefully designed gear system to tell time and sound an alarm, digital clocks have few moving parts internally. Instead, the clock and alarm will both be contained on a single circuit board. This circuit board will include a timekeeping element, such as a basic quartz clock mechanism.
AM/FM Radio
As noted, many alarm clocks are dual-function clock radios. These radios are usually built to offer an alternative to the default buzz or beep that the alarm clock would normally use. They are also able to function independently, allowing the user to listen to the radio without disrupting the function of the clock.
Speaker
Finally, all digital alarm clocks include one speaker or more, both for sounding the morning alarm and playing music from the radio. Higher-end units will offer stereo or multichannel sound, but most alarm clocks will have only one speaker, with mono sound capability.