An electric clock is a clock that is powered by electricity, as opposed to a mechanical clock which is powered by a hanging weight or a mainspring. The term is often applied to the electrically powered mechanical clocks that were used before quartz clocks were introduced in the 1980s. The first experimental electric clocks were constructed around 1840, but they were not widely manufactured until mains electric power became available in the 1890s. In the 1930s the synchronous electric clock replaced mechanical clocks as the most widely used type of clock.
Electromechanical clocks These have a traditional mechanical movement, which keeps time with an oscillating pendulum or balance wheel powered through a gear train by a mainspring, but use electricity to rewind the mainspring with an electric motor or electromagnet. This mechanism is found mostly in antique clocks.
Electric remontoire clocks In these, the gear train was turned by a small spring or weighted lever, called a remontoire, which was wound up more frequently by an electric motor or electromagnet. This mechanism was more accurate than a mainspring, because the frequent winding averaged out variations in the clock’s rate caused by the varying force of the spring as it unwound. It was used in precision pendulum clocks, and in automotive clocks until the 1970s.
Electromagnetic clocks keep time with a pendulum or balance wheel, but the pulses to keep it going are not provided by a mechanical movement and escapement linkage, but by magnetic force from an electromagnet (solenoid). This was the mechanism used in the first electric clocks, and is found in antique electric pendulum clocks. It is also found in a few modern decorative mantel and desk clocks.
Synchronous clocks rely on the 50 or 60 Hz utility frequency of the AC electric power grid as a timing source, by driving the clock gears with a synchronous motor. They essentially count cycles of the power supply. While the actual frequency may vary with loading on the grid, the total number of cycles per 24 hours is maintained rigorously constant, so that these clocks can keep time accurately for long periods, barring power cuts; over months they are more accurate than a typical quartz clock. This was the most common type of clock from the 1930s but has now been mostly replaced by quartz clocks.
Tuning Fork clocks keep time by counting the oscillations of a calibrated tuning fork with a specific frequency. These were only made in battery-powered form. Battery-powered clocks have been made using the schemes above with the obvious exception of a synchronous movement. All battery-powered clocks have been largely replaced by the lower cost quartz movement.
Quartz clocks are electric clocks which keep time by counting oscillations of a vibrating quartz crystal. They use modern low-voltage DC-powered circuitry, which may be supplied by a battery or derived from mains electricity. They are the most common type of clock today. Quartz clocks and watches as supplied by the manufacturer typically keep time with an error of a few seconds per week, although sometimes more. Inexpensive quartz movements are often specified to keep time within 30 seconds per month (1 second per day, 6 minutes per year). Lower error can be achieved by individual calibration if adjustment is possible, subject to the stability of the oscillator, particularly with change in temperature. Higher accuracy is possible at higher cost.
Radio-controlled clocks are quartz clocks which are periodically synchronized with the UTC atomic clock time scale via radio time signals broadcast by dedicated stations around the world. They are distinct from clock radios.
A circadian clock, or circadian oscillator, is a biochemical oscillator that cycles with a stable phase and is synchronized with solar time. Such a clock’s in vivo period, is necessarily almost exactly 24 hours (the earth’s current solar day). In most living things, internally synchronized circadian clocks make it possible for the organism to anticipate daily environmental changes corresponding with the day–night cycle and adjust its biology and behavior accordingly. The term circadian derives from the Latin circa (about) diem (a day), since when taken away from external cues (such as environmental light), they do not run to exactly 24 hours. Clocks in humans in a lab in constant low light, for example, will average about 24.2 hours per day, rather than 24 hours exactly.
The normal body clock oscillates with an endogenous period of exactly 24 hours, it entrains, when it receives sufficient daily corrective signals from the environment, primarily daylight and darkness. Circadian clocks are the central mechanisms that drive circadian rhythms. They consist of three major components:
a central biochemical oscillator with a period of about 24 hours that keeps time;
a series of input pathways to this central oscillator to allow entrainment of the clock;
a series of output pathways tied to distinct phases of the oscillator that regulate overt rhythms in biochemistry, physiology, and behavior throughout an organism.
The clock is reset as an organism senses environmental time cues of which the primary one is light. Circadian oscillators are ubiquitous in tissues of the body where they are synchronized by both endogenous and external signals to regulate transcriptional activity throughout the day in a tissue-specific manner. The circadian clock is intertwined with most cellular metabolic processes and it is affected by organism aging. The basic molecular mechanisms of the biological clock have been defined in vertebrate species, Drosophila melanogaster, plants, fungi, bacteria, and presumably also in Archaea.
In 2017, the Nobel Prize in Physiology or Medicine was awarded to Jeffrey C. Hall, Michael Rosbash and Michael W. Young “for their discoveries of molecular mechanisms controlling the circadian rhythm” in fruit flies.
A chess clock consists of two adjacent clocks with buttons to stop one clock while starting the other, so that the two clocks never run simultaneously. Chess clocks are used in chess and other two-player games where the players move in turn. The purpose is to keep track of the total time each player takes for their own moves, and ensure that neither player overly delays the game.
Chess clocks were first used extensively in tournament chess, and are often called game clocks. The first time that game clocks were used in a chess tournament was in the London 1883 tournament. Their use has since spread to tournament Scrabble, shogi, go, and nearly every competitive two-player board game, as well as other types of games. In a tournament, the arbiter typically places all clocks in the same orientation, so that they can easily assess games that need attention at later stages.
The simplest time control is “sudden death”, in which players must make a predetermined number of moves in a certain amount of time or forfeit the game immediately. A particularly popular variant in informal play is blitz chess, in which each player is given a short time (e.g. five minutes) on the clock in which to play the entire game.
The players may take more or less time over any individual move. The opening moves in chess are often played quickly due to their familiarity, which leaves the players more time to consider more complex and unfamiliar positions later. It is not unusual in slow chess games for a player to leave the table, but the clock of the absent player continues to run if it is their turn, or starts to run if their opponent makes a move.
The drawbacks of the mechanical clocks include accuracy and matching of the two clocks, and matching of the indicators (flags) of time expiration. Additional time cannot easily be added for more complex time controls, especially those that call for an increment or delay on every move, such as some forms of byoyomi. However, a malfunctioning analog clock is a less serious event than a malfunctioning digital clock.
From pocket watches to grandfather clocks, men have long held a fascination with keeping time in stylish and classic ways. What better way to do so than turning a handsome hardcover book into a working clock? This project is similar to what Brett did a couple years back with turning a hardcover book into a secret safe. Instead of stashing this on a bookshelf and hoping it’s not seen, however, this project is meant to be proudly displayed in your home or workplace. Coming in at under $10 and a few hours of your time at the most, this makes for a great Saturday afternoon project and an inexpensive way to decorate your apartment or man room.
Plus, with Valentine’s Day around the corner, this would make for an inexpensive but highly romantic gift for your sweetheart. Pick a book that makes her swoon (say, Pride and Prejudice) and inscribe the inside cover with a time-related sweet-nothing, like this baby from Henry Van Dyke: “Time is too slow for those who wait, too swift for those who fear, too long for those who grieve, too short for those who rejoice, but for those who love, time is eternity.” Better have some smelling salts handy.
Hardcover book. Hardcover is your best bet so that it can stand on its own. I used an old book that I never planned on reading, but another option is to find something with a unique design on the cover. Those are hard to come by these days (because they’re more money to produce), so you may need to look in antique stores. You could also use a favorite book of yours — I know it seems sacrilegious to some, but you can always buy another copy. And this way not only will you be reminded of your favorite work on a regular basis, it will serve as a great conversation piece that will allow you to share your love of it with those who visit.
A binary clock is a clock that displays the time of day in a binary format. Originally, such clocks showed each decimal digit of sexagesimal time as a binary value, but presently binary clocks also exist which display hours, minutes, and seconds as binary numbers. Most binary clocks are digital, although analog varieties exist. True binary clocks also exist, which indicate the time by successively halving the day, instead of using hours, minutes, or seconds. Similar clocks, based on Gray coded binary, also exist.
Most common binary clocks use six columns of LEDs to represent zeros and ones. Each column represents a single decimal digit, a format known as binary-coded decimal (BCD). The bottom row in each column represents 1 (or 20), with each row above representing higher powers of two, up to 23 (or 8). To read each individual digit in the time, the user adds the values that each illuminated LED represents, then reads these from left to right. The first two columns represent the hour, the next two represent the minute and the last two represent the second. Since zero digits are not illuminated, the positions of each digit must be memorized if the clock is to be usable in the dark. Binary clocks that display time in binary-coded sexagesimal also exist. Instead of representing each digit of traditional sexagesimal time with one binary number, each component of traditional sexagesimal time is represented with one binary number, that is, using up to 6 bits instead of only 4. For 24-hour binary-coded sexagesimal clocks, there are 11 or 17 LED lights to show us the time. There are 5 LEDs to show the hours, there are 6 LEDs to show the minutes, and there are 6 LEDs to show the seconds. 6 LEDs to show the seconds are not needed in 24-hour binary-coded sexagesimal clocks with 11 LED lights. A format exists also where hours, minutes and seconds are shown on three lines instead of columns as binary numbers.
A world clock is a clock which displays the time for various cities around the world. The display can take various forms:
The clock face can incorporate multiple round analogue clocks with moving hands or multiple digital clocks with numeric readouts, with each clock being labelled with the name of a major city or time zone in the world.
It could also be a picture map of the world with embedded analog or digital time-displays.
A moving circular map of the world, rotating inside a stationary 24-hour dial ring. Alternatively, the disc can be stationary and the ring moving.
Light projection onto a map representing daytime, used in the Geochron, a brand of a particular form of world clock.
There are also worldtime watches, both wrist watches and pocket watches. Sometime manufacturers of timekeepers erroneously apply the worldtime label to instruments that merely indicate time for two or a few time zones, but the term should be used only for timepieces that indicate time for all major time zones of the globe.
Manezhnaya (Russian: Манежная площадь, IPA: [mɐˈnʲeʐnəjə ˈploɕːɪtʲ], Manege Square) is a large pedestrian open space in the Tverskoy District, at the heart of Moscow. It is bound by the Hotel Moskva to the east, the State Historical Museum and the Alexander Garden to the south, the Moscow Manege to the west, and the 18th-century headquarters of the Moscow State University to the north.
The square forms a vital part of downtown Moscow, connecting Red Square (which sprawls behind the Iberian Gate immediately to the south) with the major traffic artery Tverskaya Street, which starts here and runs northwestward in the direction of Saint Petersburg. It is served by three Moscow Metro stations: Okhotny Ryad, Ploshchad Revolyutsii, and Teatralnaya.
A clock face, or dial, is the part of an analog clock (or watch) that displays the time through the use of a fixed-numbered dial or dials and moving hands. In its most basic form, recognized throughout the world, the periphery of the dial is numbered 1 through 12 indicating the hours in a 12-hour cycle, and a short hour hand makes two revolutions in a day. A long minute hand makes one revolution every hour. The face may also include a second hand, which makes one revolution per minute. The term is less commonly used for the time display on digital clocks and watches.
A second type of clock face is the 24-hour analog dial, widely used in military and other organizations that use 24-hour time. This is similar to the 12-hour dial above, except it has hours numbered 1–24 around the outside, and the hour hand makes only one revolution per day. Some special-purpose clocks, such as timers and sporting event clocks, are designed for measuring periods less than one hour. Clocks can indicate the hour with Roman numerals or Hindu–Arabic numerals, or with non-numeric indicator marks. The two numbering systems have also been used in combination, with the prior indicating the hour and the latter the minute. Longcase clocks (grandfather clocks) typically use Roman numerals for the hours. Clocks using only Arabic numerals first began to appear in the mid-18th century.
The clock face is so familiar that the numbers are often omitted and replaced with applied indices (undifferentiated hour marks), particularly in the case of watches. Occasionally, markings of any sort are dispensed with, and the time is read by the angles of the hands
Most modern clocks have the numbers 1 through 12 printed at equally spaced intervals around the periphery of the face with the 12 at the top, indicating the hour, and on many models, sixty dots or lines evenly spaced in a ring around the outside of the dial, indicating minutes and seconds. The time is read by observing the placement of several “hands”, which emanate from the centre of the dial:
A short, thick “hour” hand;
A long, thinner “minute” hand;
On some models, a very thin “second” or “sweep” hand
All the hands continuously rotate around the dial in a clockwise direction – in the direction of increasing numbers.
The second, or sweep, hand moves relatively quickly, taking a full minute (sixty seconds) to make a complete rotation from 12 to 12. For every rotation of the second hand, the minute hand will move from one minute mark to the next.
The minute hand rotates more slowly around the dial. It takes one hour (sixty minutes) to make a complete rotation from 12 to 12. For every rotation of the minute hand, the hour hand will move from one hour mark to the next.
The hour hand moves slowest of all, taking twelve hours (half a day) to make a complete rotation. It starts from “12” at midnight, makes one rotation until it is pointing at “12” again at noon, and then makes another rotation until it is pointing at “12” again at midnight of the next morning.
Even though I have a smaller countdown clock on my desk and an app on my iPhone I decided to hang one on the wall to countdown my early retirement. I love the big lighted digits. The only ding is that, unlike my smaller clock and my phone app where you enter the date and it counts down to that date, with this unit you must know the number of days and then enter that number in to start the countdown. Other than that it makes me smile when I look up and I can see the light at the end of the tunnel.
I’m seeing review after review where people are saying “it’s so small” The size is clearly stated, besides, while it’s true the case is small, the display is quite large and easy to see, so get over it. The other thing I don’t understand is people keep moaning about the set buttons on the back are unmarked. Come on people. It’s 2017. It’s basicly a clock. It’s just 3 buttons, it’s not that hard to figure out, but to be a nice guy I’m including scans of the documentation so you can always refer back to them here.
Great device and easy to learn. The only reason for not giving 5 stars is the remote. It’s small, hard to read, and doesn’t have a long range. But the clock itself does an excellent job and highly visiable.
As an adult with ADD, I keep my Time Timer at my side throughout the day. It helps me conceptualize time in a way that no other gadget ever has. Using it keeps me on track and on time better than a clock, better than an alarm or stopwatch, better than anything! I love that it makes not one sound except for a tiny beep when the time is up, because that way I can keep it by my computer as I’m working and it doesn’t distract me. If I want to know how much time I have left I might glance at it, but overall I tend to forget it’s there when I’m concentrating on my work–and that’s a good thing. There’s no “ticking”.
The apparent position of the Sun in the sky moves over the course of each day, reflecting the rotation of the Earth. Shadows cast by stationary objects move correspondingly, so their positions can be used to indicate the time of day. A sundial shows the time by displaying the position of a shadow on a (usually) flat surface, which has markings that correspond to the hours. Sundials can be horizontal, vertical, or in other orientations. Sundials were widely used in ancient times. With the knowledge of latitude, a well-constructed sundial can measure local solar time with reasonable accuracy, within a minute or two. Sundials continued to be used to monitor the performance of clocks until the modern era.
Many devices can be used to mark passage of time without respect to reference time (time of day, minutes, etc.) and can be useful for measuring duration or intervals. Examples of such duration timers are candle clocks, incense clocks and the hourglass. Both the candle clock and the incense clock work on the same principle wherein the consumption of resources is more or less constant allowing reasonably precise and repeatable estimates of time passages. In the hourglass, fine sand pouring through a tiny hole at a constant rate indicates an arbitrary, predetermined, passage of time. The resource is not consumed but re-used.
Water clocks, also known as clepsydrae (sg: clepsydra), along with the sundials, are possibly the oldest time-measuring instruments, with the only exceptions being the vertical gnomon and the day counting tally stick. Given their great antiquity, where and when they first existed is not known and perhaps unknowable. The bowl-shaped outflow is the simplest form of a water clock and is known to have existed in Babylon and in Egypt around the 16th century BC. Other regions of the world, including India and China, also have early evidence of water clocks, but the earliest dates are less certain. Some authors, however, write about water clocks appearing as early as 4000 BC in these regions of the world.
A clock is an instrument used to measure, keep, and indicate time. The clock is one of the oldest human inventions, meeting the need to measure intervals of time shorter than the natural units: the day, the lunar month, and the year. Devices operating on several physical processes have been used over the millennia.
Some predecessors to the modern clock may be considered as “clocks” that are based on movement in nature: A sundial shows the time by displaying the position of a shadow on a flat surface. There is a range of duration timers, a well-known example being the hourglass. Water clocks, along with the sundials, are possibly the oldest time-measuring instruments. A major advance occurred with the invention of the verge escapement, which made possible the first mechanical clocks around 1300 in Europe, which kept time with oscillating timekeepers like balance wheels.
Traditionally in horology, the term clock was used for a striking clock, while a clock that did not strike the hours audibly was called a timepiece. In general usage today, a “clock” refers to any device for measuring and displaying the time. Watches and other timepieces that can be carried on one’s person are often distinguished from clocks. Spring-driven clocks appeared during the 15th century. During the 15th and 16th centuries, clockmaking flourished. The next development in accuracy occurred after 1656 with the invention of the pendulum clock. A major stimulus to improving the accuracy and reliability of clocks was the importance of precise time-keeping for navigation. The electric clock was patented in 1840. The development of electronics in the 20th century led to clocks with no clockwork parts at all.
The timekeeping element in every modern clock is a harmonic oscillator, a physical object (resonator) that vibrates or oscillates at a particular frequency. This object can be a pendulum, a tuning fork, a quartz crystal, or the vibration of electrons in atoms as they emit microwaves.
Clocks have different ways of displaying the time. Analog clocks indicate time with a traditional clock face, with moving hands. Digital clocks display a numeric representation of time. Two numbering systems are in use; 24-hour time notation and 12-hour notation. Most digital clocks use electronic mechanisms and LCD, LED, or VFD displays. For the blind and use over telephones, speaking clocks state the time audibly in words. There are also clocks for the blind that have displays that can be read by touch. The study of timekeeping is known as horology.