Digital clock

A digital clock is a type of clock that displays the time digitally (i.e. in numerals or other symbols), as opposed to an analog clock, where the time is indicated by the positions of rotating 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.)

Basic digital alarm clock without a radio. The mark in the top-left of the display indicates that the time is 4:00pm, not 4:00am.
Sony Digimatic 8FC-59W radio alarm clock 20060526
A 1969 radio alarm clock (Sony Digimatic 8FC-59W) with an early mechanical-digital display


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 didn't have a watch brand at the time, his name has since been resurrected by a newly established watch manufacturer.[1]

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.[2] 13 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).[3] The German factory Aktiengesellschaft für Uhrenfabrikation Lenzkirch made such digital clocks in 1893 and 1894.[4]

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.[2]

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.[5] 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.

In the Soviet Union, the 7-segment digital clocks were known as Elektronika 7.


Digital clocks typically use the 50 or 60 hertz oscillation of AC power or a 32,768 hertz crystal oscillator as in a quartz clock 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 watches, can be switched between 12-hour and 24-hour modes. Emulations of analog-style faces often use an LCD screen, and these are also sometimes described as "digital".


Digital clock changing numbers
A digital clock's display changing numbers

To represent the time, most digital clocks use a seven-segment LED, VFD, or LCD 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.


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.[6][7]

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 clocks that have no "battery" backup, because a power outage 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 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. Commercial digital clocks are typically more reliable than consumer clocks. Multi-decade backup batteries can be used to maintain time during power loss.

LCD Clock Grey

An LCD battery-operated clock without alarm


A premium digital clock radio with digital tuning

Digital-clock-radio-basic hf

A basic digital clock radio with analog tuning

Uses of digital clocks

This digital clock has been attached to an oven.
Digital cube light clock
This digital clock reacts to temperature.

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, televisions, microwave ovens, standard ovens, 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).


  1. ^ "Home page". Archived from the original on 2015-10-01. Retrieved 2015-11-07.
  2. ^ a b Churm, Thomas M. (November 5, 2013). "A Short History of Digital Clocks and Watches". Alarm Clock Blog. Archived from the original on March 1, 2016. Retrieved 2016-02-28.
  3. ^ (in German) Imperial Patent Office (October 27, 1890). "Patent No. 54093" (PDF). German Patent and Trademark Office. Retrieved 2015-11-07.
  4. ^ "Is digital more precise?". The German Clock Museum. April 2015. Archived from the original on 2015-09-23. Retrieved 2015-11-07.
  5. ^ "The History of the Digital Watch". h2g2. April 30, 2003. Archived from the original on November 6, 2015. Retrieved 2015-11-07.
  6. ^ "Radio Controlled LED Alarm Clock Instruction Manual — SM2442" (DOC). Zeon Ltd. Archived (PDF) from the original on 2016-03-03. Retrieved 2015-11-07.
  7. ^ "Stopped Clock". TV Tropes. Archived from the original on 2015-11-05. Retrieved 2015-11-07.

External links

Ahmed Mohamed clock incident

The Ahmed Mohamed clock incident occurred when 14-year-old Ahmed Mohamed was arrested on September 14, 2015, at MacArthur High School in Irving, Texas, for bringing a reassembled digital clock to school. The incident ignited allegations of racial profiling and Islamophobia from many media and commentators.

The episode arose when Mohamed reassembled the parts of a digital clock in an 8-inch (20 cm) pencil container and brought it to school to show his teachers. His English teacher thought the device resembled a bomb, confiscated it, and reported him to the school's principal. The local police were called, and they questioned him for an hour and a half. He was handcuffed, taken into custody without permission to see his parents, and transported to a juvenile detention facility, where he was fingerprinted and a mug shot photograph was taken. He was then released to his parents. According to local police, the reason for his arrest was because they initially suspected he may have purposely caused a bomb scare. The case was not pursued further by the juvenile justice authorities, but he was suspended from school.

Following the incident, the police determined Mohamed had no malicious intent, and he was not charged with any crime. News of the incident became viral – initially on Twitter – with allegations by commentators that the actions of the school officials and police were due to their stereotyping of Mohamed based on his Sudanese ancestry and Muslim faith. Afterwards, U.S. President Barack Obama as well as other politicians, activists, technology company executives, and media personalities commented about the incident. Many of them praised Mohamed for his ingenuity and creativity, and he was invited to participate in a number of high-profile events related to encouraging youth interest in science and technology. Although Mohamed was cleared in the final police investigation, he became the subject of conspiracy theories – many of them contradictory, citing no evidence, and conflicting with established facts – which claimed that the incident was a deliberate hoax.On November 23, 2015, Ahmed's family threatened to sue the City of Irving and the school district for civil rights violations and physical and mental anguish unless they received written apologies and compensation of $15 million. This lawsuit was dismissed in May 2017 for lack of evidence. The family also sued conservative talk show hosts Glenn Beck, Ben Shapiro, and another Fox News commentator for lesser amounts on the grounds of defamation of character. Both cases were dismissed with prejudice for First Amendment free speech reasons. In late 2015, his family decided to accept a scholarship from the Qatar Foundation and move to Qatar, partially because of unsupported accusations of terrorist links and continued harassment by conspiracy theorists.

Analog modeling synthesizer

An analog modeling synthesizer is a synthesizer that generates the sounds of traditional analog synthesizers using DSP components and software algorithms. Analog modeling synthesizers simulate the behavior of the original electric and electronic circuitry in order to digitally replicate their tone.

This method of synthesis is also referred to as Virtual Analog or VA. Analog modeling synthesizers can be more reliable than their true analog counterparts since the oscillator pitch is ultimately maintained by a digital clock, and the digital hardware is typically less susceptible to temperature changes.

While analog synthesizers need an oscillator circuit for each voice of polyphony, analog modeling synthesizers don't face this problem. This means that many of them, especially the more modern models, can produce as many polyphonic voices as the CPU on which they run can handle.

Modeling synths also provide patch storage capabilities and MIDI support not found on most true analog instruments. Analog modeling synthesizers that run entirely within a host computer operating system are typically referred to as analog software synthesizers.

The term was not used until the 1990s when the Nord Lead came out.Examples of VA synthesizers include:

Access Virus line of VA synths

AKAI Miniak virtual analog synthesizer from AKAI Professional

Alesis Ion, Micron and Fusion

Arturia Origin

Clavia Nord Lead and Nord Modular series

Korg Z1, Prophecy, MS-2000, microKORG, RADIAS, R3, KingKORG, Electribe

Kurzweil PC3X

M-Audio Venom

Novation Supernova, Supernova II, Nova, A-Station, K-Station, X-Station, XioSynth, Ultranova, MiniNova

Oberheim OB12

Quasimidi Raven, Rave-O-Lution, Polymorph, Sirius

Roland JP-8000, JP-8080, V-Synth, SH-201, SH-01 Gaia, JU-06, SH-32, Aira System-8, Aira System-1

Studiologic Sledge (see Fatar)

Waldorf Q, Q+ and MicroQ

Yamaha AN1x, Yamaha Reface CS, AN200


Chronometry (from Greek χρόνος chronos, "time" and μέτρον metron, "measure") is the science of the measurement of time, or timekeeping. Chronometry applies to electronic devices, while horology refers to mechanical devices.

It should not to be confused with chronology, the science of locating events in time, which often relies upon it.

Class-T amplifier

Class T was a registered trademark for a switching (class-D) audio amplifier, used for Tripath's amplifier technologies (patent filed on Jun 20, 1996). Similar designs have now been widely adopted by different manufacturers.The covered products use a class-D amplifier combined with proprietary techniques to control the pulse width modulation to produce what is claimed to be better performance than other class-D amplifier designs. Among the publicly disclosed differences is real time control of the switching frequency depending on the input signal and amplified output. One of the amplifiers, the TA2020, was named one of the twenty-five chips that 'shook the world" by the IEEE Spectrum magazine.The control signals in Class T amplifiers may be computed using digital signal processing or fully analog techniques. Currently available implementations use a loop similar to a higher order Delta-Sigma (ΔΣ) (or sigma-delta) modulator, with an internal digital clock to control the sample comparator. The two key aspects of this topology are that (1), feedback is taken directly from the switching node rather than the filtered output, and (2), the higher order loop provides much higher loop gain at high audio frequencies than would be possible in a conventional single pole amplifier.

Financial difficulties caused Tripath to file for Chapter 11 bankruptcy protection on 8 February 2007. Tripath's stock and intellectual property were purchased later that year by Cirrus Logic.

Common year

A common year is a calendar year with 365 days, as distinguished from a leap year, which has 366. More generally, a common year is one without intercalation. The Gregorian calendar, (like the earlier Julian calendar), employs both common years and leap years to keep the calendar aligned with the tropical year, which does not contain an exact number of days.

The common year of 365 days has 52 weeks and one day, hence a common year always begins and ends on the same day of the week (for example, January 1 and December 31 fell on a Sunday in 2017) and the year following a common year will start on the subsequent day of the week. In common years, February has four weeks, so March will begin on the same day of the week. November will also begin on this day.

In the Gregorian calendar, 303 of every 400 years are common years. By comparison, in the Julian calendar, 300 out of every 400 years are common years, and in the Revised Julian calendar (used by Greece) 682 out of every 900 years are common years.

Digital clock manager

A digital clock manager (DCM) is an electronic component available on some field-programmable gate arrays (FPGAs) (notably ones produced by Xilinx). A digital clock manager is useful for manipulating clock signals inside the FPGA, and to avoid clock skew which would introduce errors in the circuit.

End-Time Mission Broadcasting Service

End-Time Mission Broadcasting Service is a radio and television broadcasting division of the Pentecostal Missionary Church of Christ (4th Watch) through its Resources for Doctrinal Empowerment and Evangelistic Ministry (ReDEEM), based in Marikina City, Philippines. EMBS owns two radio stations under the Life Radio brand, and its television network Life TV.

PMCC's media ministry can be traced back to its flagship program, Oras ng Katotohanan (ONK, Hour of Truth), which started in the 1980s on radio and television.

Flip clock

A flip clock is an electromechanical, digital time keeping device with the time indicated by numbers that are sequentially revealed by a split-flap display. The study, collection and repair of flip clocks is termed horopalettology [From horology - The study and measurement of time and palette - from the Italian "Orologi a palette" - Italian for flip clock]. People interested in the collection, restoration, buying and selling of flip clocks are known as horopalettologists.


The terms foobar (), or foo and others are used as metasyntactic variables and placeholder names in computer programming or computer-related documentation. They have been used to name entities such as variables, functions, and commands whose exact identity is unimportant and serve only to demonstrate a concept.


HD2IOA is the callsign of a time signal radio station operated by the Navy of Ecuador. The station is located at Guayaquil, Ecuador and transmits in the HF band on 3.81 and 7.6 MHz.The transmission is in AM mode with only the lower sideband (part of the time H3E and the rest H2B/H2D) and consists of 780 Hz tone pulses repeated every ten seconds and voice announcements in Spanish.

While sometimes this station is described as defunct, reception reports of this station on 3.81 MHz appear regularly at the Utility DX Forum.

Intercalation (timekeeping)

Intercalation or embolism in timekeeping is the insertion of a leap day, week, or month into some calendar years to make the calendar follow the seasons or moon phases. Lunisolar calendars may require intercalations of both days and months.

My Pretty Pony

"My Pretty Pony" is a short story written by Stephen King and illustrated by the artist Barbara Kruger. It was the sixth publication in the Whitney Museum of American Art artist and writer series. An original limited coffee table book edition of 250 was published in 1989 and was an oversized fine press slip-cased book with stainless steel faced boards and digital clock inset into the front cover. A trade edition of 15,000 was later published by Alfred A. Knopf. In 1993, the story was included in King's collection Nightmares & Dreamscapes.


The Omnibot (オムニボット) is a toy robot originally manufactured by Tomy in the mid-1980s. The name then came to apply to the successful line of robots manufactured by the company. The initial Omnibot was announced with expectations of restoring popular interest in robots, at a time when it was becoming obvious that robots with advanced AI such as R2-D2 were still a long way away. A more advanced version of the Omnibot was called the Omnibot 2000 and did not have a plastic bubble over its head. With the success of the Omnibots, the Omnibot range quickly expanded. After the North American video game crash of 1983 and its debilitating effect on the entire nascent home electronics industry, the Omnibot faded away but it was revived in the early 2000s. The latest version of the Omnibot is the i-SOBOT.

Both the Omnibot and the more advanced Omnibot 2000 had a cassette tape player built into the chest area of the robot, which slid out like a drawer to reveal the cassette and could record and play back sequences of commands, as well as regular audio recordings. The built in digital clock with timers and alarms allowed the playback of movement recordings at specified times, such as moving into the bedroom in the morning. Both robots were able to broadcast speech from the remote control handset through a speaker on the robot, and both were shipped with a cardboard "home" base which was suggested to be taped to the floor and used as a reference point for programming.

Both Omnibot and the Omnibot 2000 could carry light objects. The Omnibot carried a specially made tray which slotted into its claws, and the Omnibot 2000 had a tray which slotted into its motorised "accessory panel", allowing the tray to revolve cups and glasses into the reach of the arm.

The Omnibot 2000 was 25 inches tall, powered by a 6-volt lead–acid battery and two AA batteries. Its right arm was controllable. The user could control its shoulder, elbow, wrist and fingers, the left arm being a poseable "dummy".

Unfortunately, losing the remote control unit for an Omnibot meant that the robot was virtually useless outside of the clock and cassette deck based functions.

Two lesser known robots in the Omnibot range were the Omnibot OOM and the Omniwagon. The Omnibot OOM was shaped like a standard Omnibot except with the addition of a spherical head, its remote controller including a basic form of voice-control. The Omniwagon was merely a remote controlled drive unit and wheels from an omnibot with a flat surface on top to carry objects.


The Rheinturm (pronounced [ˈʁaɪ̯ntʊʁm]) (Rhine Tower) is a 240.5-metre-high (789 ft) concrete telecommunications tower in Düsseldorf, capital of the federal state (Bundesland) of North Rhine-Westphalia, Germany. Construction commenced in 1979 and finished in 1981. The Rheinturm carries aerials for directional radio, FM and TV transmitters. It stands 174.5 metres high and houses a revolving restaurant and an observation deck at a height of 170 metres. It is the tallest building in Düsseldorf.The Rheinturm was inaugurated on 1 December 1981. It contains 7,500 cubic metres of concrete and weighs 22,500 tons. Before October 15, 2004, when an aerial antenna for DVB-T was mounted, it was 234.2 metres high.

The observation deck is open to public, daily from 10:00 AM to 11:30 PM. As a special attraction, a light sculpture on its shaft works as a clock. This sculpture was designed by Horst H. Baumann and is called Lichtzeitpegel (light time level). The light sculpture on the Rheinturm is the largest digital clock in the world.

Split Second (TV series)

Split Second is a 2004 Hong Kong crime thriller television drama produced by TVB and Thailand's TV3, with Marco Law serving as the executive producer. It ran from October 4, 2004 to November 12, 2004, with the total of 30 episodes.

This show uses a format similar to the American series 24. Each one-hour episode represents one day in the show's timeline, and an on-screen digital clock appears in the show regularly to remind viewers the time in the storyline.

Standby power

Standby power, also called vampire power, vampire draw, phantom load, ghost load or leaking electricity ("phantom load" and "leaking electricity" are defined technical terms with other meanings, adopted for this different purpose), refers to the way electric power is consumed by electronic and electrical appliances while they are switched off (but are designed to draw some power) or in standby mode. This only occurs because some devices claimed to be "switched off" on the electronic interface, but are in a different state from switching off at the plug, or disconnecting from the power point, which can solve the problem of standby power completely. In fact, switching off at the power point is effective enough, there is no need to disconnect all devices from the power point. Some such devices offer remote controls and digital clock features to the user, while other devices, such as power adapters for disconnected electronic devices, consume power without offering any features (sometimes called no-load power). All of the above examples, such as the remote control, digital clock functions and—in the case of adapters, no-load power—are switched off just by switching off at the power point. However, for some devices with built-in internal battery, such as a phone, the standby functions can be stopped by removing the battery instead.

In the past, standby power was largely a non-issue for users, electricity providers, manufacturers, and government regulators. In the first decade of the twenty-first century, awareness of the issue grew and it became an important consideration for all parties. Up to the middle of the decade, standby power was often several watts or even tens of watts per appliance. By 2010, regulations were in place in most developed countries restricting standby power of devices sold to one watt (and half that from 2013).

Time code ambiguity

In telecommunication, time code ambiguity is the shortest interval between successive repetitions of the same time code value.

For example, in a time code in which year-of-century (the '72' in 10/04/72) is the most slowly changing field, the time code ambiguity would be 100 years; it is ambiguous whether this value refers to a date in 1872, 1972 or some other century. For a digital clock in which hours and minutes up to a maximum of 11:59 are displayed, the time code ambiguity would be 12 hours.

The Year 2000 problem is an example of the pitfalls of time code ambiguity. Very often dates are now recorded with 4 digit years (10/04/1972). Assuming that the use of a 4-digit year field would continue, even in the far future, this would change the time code ambiguity from 100 years to 10 000 years.

Transit 3B

Transit 3B was an American satellite which was launched in 1961 and operated by the United States Navy. It was a replacement for Transit 3A, which was lost in a launch failure the previous year. It carried instruments to demonstrate navigation and timing systems, and study geodesy to support the development of the Transit satellite navigation system.The launch of Transit 3B was conducted at 03:45 UTC on 22 February 1961, using a Thor DM-21 Ablestar rocket flying from Launch Complex 17B at the Cape Canaveral Air Force Station. The LOFTI-1 satellite was launched aboard the same rocket. The rocket and upper stage used had the serial numbers Thor 313 and Ablestar 007 respectively. The launch resulted in a partial failure, with the spacecraft being placed in a more eccentric orbit than planned, and failing to separate from the upper stage.Transit 3B was a 113-kilogram (249 lb) spacecraft, which was powered by 6,600 solar cells charging a nickel-cadmium battery. It ended up in a low Earth orbit with a perigee of 167 kilometres (104 mi), an apogee of 1,002 kilometres (623 mi), and 28.3 degrees of inclination. It had an orbital period of 96.4 minutes. Due to the low perigee of its orbit, Transit 3B decayed quickly, and reentered the atmosphere on 30 March 1961, less than 37 days after launch. Despite being in the wrong orbit and operating for less time than had been planned, some useful data was returned from the mission.The systems demonstrated by Transit 3B included a digital clock to control timing signals, uploading programs into the onboard computer's memory whilst in orbit, data retention and FM encoding, and the use of phase modulation for data transmission without affecting the satellite's Doppler signal. The satellite's computer had a memory capacity of 48 bytes.

Yesterday (time)

Yesterday is a temporal construct of the relative past; literally of the day before the current day (today), or figuratively of earlier periods or times, often but not always within living memory.

Powerline synchronized
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