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Digital clock

Digital clock

Overview


A digital clock is a type of clock
Clock
A clock is an instrument used to indicate, keep, and co-ordinate time. The word clock is derived ultimately from the Celtic words clagan and clocca meaning "bell". A silent instrument missing such a mechanism has traditionally been known as a timepiece...

 that displays the time digital
Digital
A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...

ly, i.e. in cyphers, as opposed to an analog clock, where the time is displayed by hands. Digital clocks are often associated with electronic drives, but the "digital" description refers only to the display, not to the drive mechanism. (Both analog and digital clocks can be driven either mechanically or electronically, but "clockwork" mechanisms with digital displays are rare.) The biggest digital clock is the Lichtzeitpegel ("Light Time Level") on the television tower Rheinturm Düsseldorf
Rheinturm Düsseldorf
The Rheinturm is a 240.5 metre high concrete telecommunications tower in Düsseldorf, capital of the federal state of North Rhine-Westphalia, Germany. Construction commenced in 1979 and finished in 1981. The Rheinturm carries aerials for directional radio, FM and TV transmitters...

, Germany.

Perhaps the earliest digital timepieces were Plato clocks.
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Encyclopedia


A digital clock is a type of clock
Clock
A clock is an instrument used to indicate, keep, and co-ordinate time. The word clock is derived ultimately from the Celtic words clagan and clocca meaning "bell". A silent instrument missing such a mechanism has traditionally been known as a timepiece...

 that displays the time digital
Digital
A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...

ly, i.e. in cyphers, as opposed to an analog clock, where the time is displayed by hands. Digital clocks are often associated with electronic drives, but the "digital" description refers only to the display, not to the drive mechanism. (Both analog and digital clocks can be driven either mechanically or electronically, but "clockwork" mechanisms with digital displays are rare.) The biggest digital clock is the Lichtzeitpegel ("Light Time Level") on the television tower Rheinturm Düsseldorf
Rheinturm Düsseldorf
The Rheinturm is a 240.5 metre high concrete telecommunications tower in Düsseldorf, capital of the federal state of North Rhine-Westphalia, Germany. Construction commenced in 1979 and finished in 1981. The Rheinturm carries aerials for directional radio, FM and TV transmitters...

, Germany.

History


Perhaps the earliest digital timepieces were Plato clocks. These spring-wound pieces consisted of a glass cylinder with a column inside, affixed to which were small digital cards with numbers printed on them, which flipped as time passed. The Plato clocks were introduced at the St. Louis World Fair in 1904, produced by Ansonia Clock Company. Eugene Fitch of New York patented the clock design in 1903.

Josef Pallweber, a Swiss timepiece maker born in Salzburg, Austria, created and produced a mechanic-digital clock model in 1956. The earliest patent for a digital clock was held in the United States by D.E Protzmann and others. Dated October 23, 1956, this patent describes a digital alarm clock. D.E Protzmann and his associates also patented another digital clock in 1970, which was said to use a minimal amount of moving parts. Two side-plates held digital numerals between them, while an electric motor and cam gear outside controlled movement.

In 1970, the first digital wristwatch with an LED display was mass-produced. Called the Pulsar, and produced by the Hamilton Watch Company, this watch was hinted at two years prior when the same company created a prototype digital watch for Kubrick's 2001: A Space Odyssey. Throughout the 1970s, despite the initial hefty cost of digital watches, the popularity of said devices steadily rose.

Over the years, many different types of digital alarm clocks have been developed. Novelty clocks, such as the Gun O'Clock, require more involved actions to deactivate the alarm.

Construction


Digital clocks typically use the 50 or 60 hertz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....

 oscillation of AC power
AC power
Power in an electric circuit is the rate of flow of energy past a given point of the circuit. In alternating current circuits, energy storage elements such as inductance and capacitance may result in periodic reversals of the direction of energy flow...

 or a 32,768 hertz crystal oscillator
Crystal oscillator
A crystal oscillator is an electronic oscillator circuit that uses the mechanical resonance of a vibrating crystal of piezoelectric material to create an electrical signal with a very precise frequency...

 as in a quartz clock
Quartz clock
A quartz clock is a clock that uses an electronic oscillator that is regulated by a quartz crystal to keep time. This crystal oscillator creates a signal with very precise frequency, so that quartz clocks are at least an order of magnitude more accurate than good mechanical clocks...

 to keep time. Most digital
Digital
A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...

 clocks display the hour of the day in 24 hour format
24-hour clock
The 24-hour clock is a convention of time keeping in which the day runs from midnight to midnight and is divided into 24 hours, indicated by the hours passed since midnight, from 0 to 23. This system is the most commonly used time notation in the world today...

; in the United States and a few other countries, a more commonly used hour sequence option is 12 hour format
12-hour clock
The 12-hour clock is a time conversion convention in which the 24 hours of the day are divided into two periods called ante meridiem and post meridiem...

(with some indication of AM or PM). Emulations of analog-style faces often use an LCD screen, and these are also sometimes described as "digital".

Displays




To represent the time, most digital clocks use a seven-segment
Seven-segment display
A seven-segment display , or seven-segment indicator, is a form of electronic display device for displaying decimal numerals that is an alternative to the more complex dot-matrix displays...

 LED
LEd
LEd is a TeX/LaTeX editing software working under Microsoft Windows. It is a freeware product....

, VFD
Vacuum fluorescent display
A vacuum fluorescent display is a display device used commonly on consumer-electronics equipment such as video cassette recorders, car radios, and microwave ovens. Invented in Japan in 1967, the displays became common on calculators and other consumer electronics devices...

, or LCD display for each of four digits
Numerical digit
A digit is a symbol used in combinations to represent numbers in positional numeral systems. The name "digit" comes from the fact that the 10 digits of the hands correspond to the 10 symbols of the common base 10 number system, i.e...

. 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.

Setting




If people find difficulty in setting the time in some designs of digital clocks in electronic devices where the clock is not a critical function, they may not be set at all, displaying the default after powered on, 00:00 or 12:00 http://www.zeonltd.co.uk/instructions/Gifts%20and%20Gadgets/Science%20Museum/SM2442%20-%20R.C%20LED%20Alarm%20Clock.pdfhttp://tvtropes.org/pmwiki/pmwiki.php/Main/StoppedClock.

Digital clocks that run on mains electricity and have no battery must be reset every time the power is cut off or if they are moved. Even if power is cut off for a second, most clocks will still have to be reset. This is a particular problem with alarm clock
Alarm clock
An alarm clock is a clock that is designed to make a loud sound at a specific time. The primary use of these clocks is to awaken people from their night's sleep or short naps; they are sometimes used for other reminders as well. To stop the sound, a button or handle on the clock is pressed; but...

s that have no "battery" backup, because even a very brief power outage
Power outage
A power outage is a short- or long-term loss of the electric power to an area.There are many causes of power failures in an electricity network...

 during the night usually results in the clock failing to trigger the alarm in the morning.

To reduce the problem, many devices designed to operate on household electricity incorporate a battery
Battery (electricity)
An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power...

 backup to maintain the time during power outages and during times of disconnection from the power supply. More recently, some devices incorporate a method for automatically setting the time, such as using a broadcast radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...

 time signal
Time signal
A time signal is a visible, audible, mechanical, or electronic signal used as a reference to determine the time of day.-Audible and visible time signals:...

 from an atomic clock
Atomic clock
An atomic clock is a clock that uses an electronic transition frequency in the microwave, optical, or ultraviolet region of the electromagnetic spectrum of atoms as a frequency standard for its timekeeping element...

, getting the time from an existing satellite television
Satellite television
Satellite television is television programming delivered by the means of communications satellite and received by an outdoor antenna, usually a parabolic mirror generally referred to as a satellite dish, and as far as household usage is concerned, a satellite receiver either in the form of an...

 or computer
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...

 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.

Uses



  • Because digital clocks can be very small and inexpensive devices that enhance the popularity of product designs, they are often incorporated into all kinds of devices such as cars, radios, television
    Television
    Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...

    s, microwave oven
    Microwave oven
    A microwave oven is a kitchen appliance that heats food by dielectric heating, using microwave radiation to heat polarized molecules within the food...

    s, standard oven
    Oven
    An oven is a thermally insulated chamber used for the heating, baking or drying of a substance. It is most commonly used for cooking. Kilns, and furnaces are special-purpose ovens...

    s, computers and cell phones. Sometimes their usefulness is disputed: a common complaint is that when time has to be set to Daylight Saving Time, many household clocks have to be readjusted. The incorporation of automatic synchronisation by a radio time signal is reducing this problem (see Radio clock
    Radio clock
    A radio clock or radio-controlled clock is a clock that is synchronized by a time code bit stream transmitted by a radio transmitter connected to a time standard such as an atomic clock...

    ).

External links