
A digital clock displays the time
digitally (i.e. in numerals or other symbols), as opposed to an
analogue clock
A clock or chronometer is a device that measures and displays time. The clock is one of the oldest human inventions, meeting the need to measure intervals of time shorter than the natural units such as the day, the lunar month, and the yea ...
.
Digital clocks are often associated with electronic drives, but the "digital" description refers only to the display, not to the drive mechanism. (Both analogue and digital clocks can be driven either mechanically or electronically, but "clockwork" mechanisms with digital displays are rare.)
History
The first digital pocket watch was the invention of
Austrian engineer Josef Pallweber who created his "jump-hour" mechanism in 1883. Instead of a conventional dial, the jump-hour featured two windows in an enamel dial, through which the hours and minutes are visible on rotating discs. The second hand remained conventional. By 1885, Pallweber mechanism was already on the market in pocket watches by
Cortébert and
IWC; arguably contributing to the subsequent rise and commercial success of IWC. The principles of Pallweber jump-hour movement had appeared in wristwatches by the 1920s (Cortébert) and are still used today (
Chronoswiss Digiteur). While the original inventor did not have a watch brand at the time, his name has since been resurrected by a newly established watch manufacturer.
Plato clocks used a similar idea but a different layout. 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.
Thirteen years earlier, Josef Pallweber had patented the same invention using digital cards (different from his 1885 patent using moving disks) in Germany (DRP No. 54093).
The German factory
Aktiengesellschaft für Uhrenfabrikation Lenzkirch
Aktiengesellschaft für Uhrenfabrikation Lenzkirch (''Public company for clockmaking Lenzkirch'') was founded in 1851 in the village of Lenzkirch in Baden by Eduard Hauser who had trained in France and Switzerland. It is in the tradition of Blac ...
made such digital clocks in 1893 and 1894.
The earliest patent for a digital alarm clock was registered by D. E. Protzmann and others on October 23, 1956, in the United States. 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 unveiled on
The Tonight Show Starring Johnny Carson
''The Tonight Show Starring Johnny Carson'' is an American television talk show broadcast by NBC. The show was the third installment of ''The Tonight Show''. Hosted by Johnny Carson, it aired from October 1, 1962 to May 22, 1992, replacing ''T ...
, although it was not released until 1972.
[ https://pabook.libraries.psu.edu/literary-cultural-heritage-map-pa/feature-articles/pulsar-revolution-display-technology#:~:text=The%20Pulsar%20was%20the%20first,watch%20with%20no%20moving%20parts. ] Called the Pulsar, and produced by the
Hamilton Watch Company
The Hamilton Watch Company is a Switzerland, Swiss manufacturer of wristwatches based in Biel/Bienne, Bienne, Switzerland. Founded in 1892 as an American firm, the Hamilton Watch Company ended American manufacture in 1969, shifting manufacturing ...
, this watch was hinted at two years prior when the same company created a non-function digital watch prop (with a main analogue face but a secondary digital display) for Kubrick's ''
2001: A Space Odyssey''.
Construction
Digital clocks typically use the 50 or 60
hertz
The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or Cycle per second, cycle) per second. The hertz is an SI derived unit whose formal expression in ter ...
oscillation of
AC power
In an electric circuit, instantaneous power is the time rate of flow of energy past a given point of the circuit. In alternating current circuits, energy storage elements such as inductors and capacitors may result in periodic reversals of the d ...
or a 32,768 hertz
crystal oscillator
A crystal oscillator is an electronic oscillator Electrical circuit, circuit that uses a piezoelectricity, piezoelectric crystal as a frequency selective surface, frequency-selective element. The oscillator frequency is often used to keep trac ...
as in a
quartz clock
Quartz clocks and quartz watches are timepieces that use an electronic oscillator regulated by a quartz crystal to keep time. The crystal oscillator, controlled by the resonant mechanical vibrations of the quartz crystal, creates a signal with ...
to keep time. Most digital clocks display the hour of the day in
24-hour format; in the United States and a few other countries, a commonly used hour sequence option is
12-hour format (with some indication of AM or PM). Some timepieces, such as many
digital watch
A watch is a timepiece carried or worn by a person. It is designed to maintain a consistent movement despite the motions caused by the person's activities. A wristwatch is worn around the wrist, attached by a watch strap or another type of ...
es, can be switched between 12-hour and 24-hour modes. Emulations of analog-style faces often use an
LCD
A liquid-crystal display (LCD) is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers to display information. Liquid crystals do not em ...
screen, and these are also sometimes described as "digital".
Displays

To represent time, most digital clocks use a
seven-segment LED
A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (corresp ...
,
VFD, or LCD for each of the 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. Older digital clocks used numbers painted on wheels, or
a split-flap display. High-end digital clocks use
dot matrix displays and use animations for digit changes.
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.
Because they run on electricity, digital clocks often need to be reset whenever the power is cut off, even for a very brief period of time. This is a particular problem with
alarm clock
An alarm clock or alarm is a clock that is designed to alert an individual or group of people at a specified time. The primary function of these clocks is to awaken people from their night's sleep or short naps; they can sometimes be used for o ...
s that have no "battery" backup, because a
power outage
A power outage, also called a blackout, a power failure, a power blackout, a power loss, a power cut, or a power out is the complete loss of the electrical power network supply to an end user.
There are many causes of power failures in an el ...
during the night usually prevents the clock from triggering the alarm in the morning.
To reduce the problem, many devices designed to operate on household electricity incorporate a
battery 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 is the technology of communicating using radio waves. Radio waves are electromagnetic waves of frequency between 3 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connec ...
time signal
A time signal is a visible, audible, mechanical, or electronic signal used as a reference to determine the time of day.
Church bells or voices announcing hours of prayer gave way to automatically operated chimes on public clocks; however, au ...
from an
atomic clock
An atomic clock is a clock that measures time by monitoring the resonant frequency of atoms. It is based on atoms having different energy levels. Electron states in an atom are associated with different energy levels, and in transitions betwee ...
, getting the time from an existing
satellite television
Satellite television is a service that delivers television programming to viewers by relaying it from a communications satellite orbiting the Earth directly to the viewer's location.ITU Radio Regulations, Section IV. Radio Stations and Systems ...
or
computer
A computer is a machine that can be Computer programming, programmed to automatically Execution (computing), carry out sequences of arithmetic or logical operations (''computation''). Modern digital electronic computers can perform generic set ...
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.
Commercial digital clocks are typically more reliable than consumer clocks. Multi-decade backup batteries can be used to maintain time during power loss.
File:LCD Clock Grey.jpg, An LCD battery-operated clock without alarm
File:Digital-clock-radio-premium.jpg, A premium digital clock radio with digital tuning
File:Digital-clock-radio-basic hf.jpg, A basic digital clock radio with analog tuning
File:LCD_Clock.jpg, Transflective LCD battery-operated clock with radio time setting
File:Nixie clock.jpg, Telefunken
Telefunken was a German radio and television producer, founded in Berlin in 1903 as a joint venture between Siemens & Halske and the ''AEG (German company), Allgemeine Elektrizitäts-Gesellschaft'' (AEG) ("General electricity company").
Prior to ...
nixie tube
A Nixie tube ( ), or cold cathode display, is an electronics, electronic device used for display device, displaying numerals or other information using glow discharge.
The glass tube contains a wire-mesh anode and multiple cathodes, shaped like ...
clock
File:Orologio Solari Cifra 3.jpg, Solari ''Cifra 3
The Cifra 3 is a digital flip clock manufactured by Solari di Udine, S.p.A., Italy. It was designed by Italian architect (1923–2003) in 1965, with contributions from Belgian inventor John Myer and typography design by Massimo Vignelli. The Cif ...
'' designed by (1965)
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 (TV) is a telecommunication medium for transmitting moving images and sound. Additionally, the term can refer to a physical television set rather than the medium of transmission. Television is a mass medium for advertising, ...
s,
microwave oven
A microwave oven, or simply microwave, is an electric oven that heats and cooks food by exposing it to electromagnetic radiation in the microwave frequency range. This induces Dipole#Molecular dipoles, polar molecules in the food to rotate and ...
s, standard
oven
upA double oven
A ceramic oven
An oven is a tool that is used to expose materials to a hot environment. Ovens contain a hollow chamber and provide a means of heating the chamber in a controlled way. In use since antiquity, they have been use ...
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 synchronization by a radio time signal is reducing this problem (see
Radio clock
A radio clock or radio-controlled clock (RCC), and often colloquially (and incorrectly) referred to as an "atomic clock", is a type of Quartz clock, quartz clock or watch that is automatically Synchronization, synchronized to a time code transmi ...
). Smart digital clocks, in addition to displaying time, scroll additional information such as weather and notifications.
References
External links
History of the Digital WatchMuseum of Vintage Rare Digital LCD Wrist Watches
{{Authority control
Austrian inventions
Clock designs
Clock
A clock or chronometer is a device that measures and displays time. The clock is one of the oldest Invention, human inventions, meeting the need to measure intervals of time shorter than the natural units such as the day, the lunar month, a ...