|
Clock Network
A clock network or clock system is a set of synchronized clocks designed to always show exactly the same time by communicating with each other. Clock networks usually consist of a central master clock kept in sync with an official time source, and one or more slave clocks which receive and display the time from the master. Synchronization sources The master clock in a clock network can receive accurate time in a number of ways: through the United States GPS satellite constellation, a Network Time Protocol server, the CDMA cellular phone network, a modem connection to a time source, or by listening to radio transmissions from WWV or WWVH, or a special signal from an upstream broadcast network. Some master clocks don't determine the time automatically. Instead, they rely on an operator to manually set them. Clock networks in critical applications often include a backup source to receive the time, or provisions to allow the master clock to maintain the time even if it loses ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Master Clock System
Master or masters may refer to: Ranks or titles *Ascended master, a term used in the Theosophical religious tradition to refer to spiritually enlightened beings who in past incarnations were ordinary humans *Grandmaster (chess), National Master, International Master, FIDE Master, Candidate Master, all ranks of chess player *Grandmaster (martial arts) or Master, an honorary title *Grand master (order), a title denoting the head of an order or knighthood *Grand Master (Freemasonry), the head of a Grand Lodge and the highest rank of a Masonic organization *Maestro, an orchestral conductor, or the master within some other musical discipline *Master, a Names and titles of Jesus in the New Testament#Master, title of Jesus in the New Testament *Master or shipmaster, the sea captain of a merchant vessel *Master (college), head of a college *Master (form of address), an English honorific for boys and young men *Master (judiciary), a judicial official in the courts of common law jurisdictio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Master Control
Master control is the technical hub of a broadcast operation common among most over-the-air television stations and television networks. It is distinct from a production control room (PCR) in television studios where the activities such as switching from camera to camera are coordinated. A transmission control room (TCR) is usually smaller in size and is a scaled down version of centralcasting. Master control is the final point before a signal is transmitted over-the-air for terrestrial television or cablecast, satellite provider for broadcast, or sent on to a cable television operator. Television master control rooms include banks of video monitors, satellite receivers, videotape machines, video servers, transmission equipment, and, more recently, computer broadcast automation equipment for recording and playback of television programming. Master control is generally staffed with one or two master control operators around-the-clock to ensure continuous operation. Master cont ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Master Clock
Master or masters may refer to: Ranks or titles * Ascended master, a term used in the Theosophical religious tradition to refer to spiritually enlightened beings who in past incarnations were ordinary humans *Grandmaster (chess), National Master, International Master, FIDE Master, Candidate Master, all ranks of chess player *Grandmaster (martial arts) or Master, an honorary title * Grand master (order), a title denoting the head of an order or knighthood *Grand Master (Freemasonry), the head of a Grand Lodge and the highest rank of a Masonic organization *Maestro, an orchestral conductor, or the master within some other musical discipline *Master, a title of Jesus in the New Testament *Master or shipmaster, the sea captain of a merchant vessel *Master (college), head of a college *Master (form of address), an English honorific for boys and young men *Master (judiciary), a judicial official in the courts of common law jurisdictions *Master mariner, a licensed mariner who is qualif ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Clock
A radio clock or radio-controlled clock (RCC), and often (incorrectly) referred to as an atomic clock is a type of quartz clock or watch that is automatically synchronized to a time code transmitted by a radio transmitter connected to a time standard such as an atomic clock. Such a clock may be synchronized to the time sent by a single transmitter, such as many national or regional time transmitters, or may use the multiple transmitters used by satellite navigation systems such as Global Positioning System. Such systems may be used to automatically set clocks or for any purpose where accurate time is needed. RC clocks may include any feature available for a clock, such as alarm function, display of ambient temperature and humidity, broadcast radio reception, etc. One common style of radio-controlled clock uses time signals transmitted by dedicated terrestrial longwave radio transmitters, which emit a time code that can be demodulated and displayed by the radio controlled clock. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Synchronization In Telecommunications
Many services running on modern digital telecommunications networks require accurate synchronization for correct operation. For example, if telephone exchanges are not synchronized, then bit slips will occur and degrade performance. Telecommunication networks rely on the use of highly accurate primary reference clocks which are distributed network-wide using synchronization links and synchronization supply units. Ideally, clocks in a telecommunications network are synchronous, controlled to run at identical rates, or at the same mean rate with a fixed relative phase displacement, within a specified limited range. However, they may be mesochronous in practice. In common usage, mesochronous networks are often described as ''synchronous''. Components Primary reference clock (PRC) Modern telecommunications networks use highly accurate primary master clocks that must meet the international standards requirement for long term frequency accuracy better than 1 part in 1011. To get ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NTP Clock Strata
The Network Time Protocol (NTP) is a networking protocol for clock synchronization between computer systems over packet-switched, variable- latency data networks. In operation since before 1985, NTP is one of the oldest Internet protocols in current use. NTP was designed by David L. Mills of the University of Delaware. NTP is intended to synchronize all participating computers to within a few milliseconds of Coordinated Universal Time (UTC). It uses the intersection algorithm, a modified version of Marzullo's algorithm, to select accurate time servers and is designed to mitigate the effects of variable network latency. NTP can usually maintain time to within tens of milliseconds over the public Internet, and can achieve better than one millisecond accuracy in local area networks under ideal conditions. Asymmetric routes and network congestion can cause errors of 100 ms or more. The protocol is usually described in terms of a client–server model, but can as easily be u ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Greenwich Time Signal
The Greenwich Time Signal (GTS), popularly known as the pips, is a series of six short tones (or "pips") broadcast at one-second intervals by many BBC Radio stations. The pips were introduced in 1924 and have been generated by the BBC since 1990 to mark the precise start of each hour. Their utility in calibration is diminishing as digital broadcasting entails time lags. Structure There are six pips (short beeps) in total, which occur on each of the 5 seconds leading up to the hour and on the hour itself. Each pip is a 1 k Hz tone (about a fifth of a semitone above musical B5) the first five of which last a tenth of a second each, while the final pip lasts half a second. The actual moment when the hour changes – the "on-time marker" – is at the very beginning of the last pip. When a leap second occurs (exactly one second before midnight UTC), it is indicated by a seventh pip. In this case the first pip occurs at 23:59:55 (as usual) and there is a sixth short pip a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Longcase Clock
A grandfather clock (also a longcase clock, tall-case clock, grandfather's clock, or floor clock) is a tall, freestanding, weight-driven pendulum clock with the pendulum held inside the tower or waist of the case. Clocks of this style are commonly 1.8–2.4 metres (6–8 feet) tall with an enclosed pendulum and weights suspended by either cables or chains which have to be calibrated occasionally to keep the proper time. The case often features elaborately carved ornamentation on the hood (or bonnet), which surrounds and frames the dial, or clock face. The English clockmaker William Clement is credited with the development of this form in 1670. Until the early 20th century, pendulum clocks were the world's most accurate timekeeping technology, and longcase clocks, due to their superior accuracy, served as time standards for households and businesses. Today they are kept mainly for their decorative and antique value, having been widely replaced by both analog and digital ti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pendulum Clock
A pendulum clock is a clock that uses a pendulum, a swinging weight, as its timekeeping element. The advantage of a pendulum for timekeeping is that it is a harmonic oscillator: It swings back and forth in a precise time interval dependent on its length, and resists swinging at other rates. From its invention in 1656 by Christiaan Huygens, inspired by Galileo Galilei, until the 1930s, the pendulum clock was the world's most precise timekeeper, accounting for its widespread use. Throughout the 18th and 19th centuries, pendulum clocks in homes, factories, offices, and railroad stations served as primary time standards for scheduling daily life, work shifts, and public transportation. Their greater accuracy allowed for the faster pace of life which was necessary for the Industrial Revolution. The home pendulum clock was replaced by less-expensive, synchronous electric clock, synchronous, electric clocks in the 1930s and '40s. Pendulum clocks are now kept mostly for their Interior ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 between such states they interact with a very specific frequency of electromagnetic radiation. This phenomenon serves as the basis for the International System of Units' (SI) definition of a second:The second, symbol s, is the SI unit of time. It is defined by taking the fixed numerical value of the caesium frequency, \Delta \nu_\mathsf, the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom, to be when expressed in the unit Hz, which is equal to s−1. This definition is the basis for the system of International Atomic Time (TAI), which is maintained by an ensemble of atomic clocks around the world. The system of Coordinated Universal Time, Coordinated Universal Time (UTC) that is the basis of civil time implements ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shepherd Gate Clock
The Shepherd Gate Clock () is mounted on the wall outside the gate of the Royal Observatory, Greenwich building in Greenwich, Greater London. The clock, an early example of an electrically connected clock system, was a sympathetic clock mechanism controlled by electric pulses transmitted by a motor clock inside the main building. The network of 'sympathetic clocks' was constructed and installed by Charles Shepherd in 1852. The clock by the gate was probably the first to display Greenwich Mean Time to the public, and is unusual in using the 24-hour analog dial. Also it originally showed astronomical time which started at 12 noon not midnight. The gate clock distributed the time publicly; another time signal of the observatory was the time ball, since 1833. The time ball only signalled 1.00pm (13:00), but could be seen from afar. Eventually the idea of distributing time signals via wires led to more and more electrical distribution of time signals by this method. Time signals, b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Royal Greenwich Observatory
The Royal Observatory, Greenwich (ROG; known as the Old Royal Observatory from 1957 to 1998, when the working Royal Greenwich Observatory, RGO, temporarily moved south from Greenwich to Herstmonceux) is an observatory situated on a hill in Greenwich Park in south east London, overlooking the River Thames to the north. It played a major role in the history of astronomy and navigation, and because the Prime Meridian passes through it, it gave its name to Greenwich Mean Time, the precursor to today's Coordinated Universal Time (UTC). The ROG has the IAU observatory code of 000, the first in the list. ROG, the National Maritime Museum, the Queen's House and the clipper ship ''Cutty Sark'' are collectively designated Royal Museums Greenwich. The observatory was commissioned in 1675 by King Charles II, with the foundation stone being laid on 10 August. The old hilltop site of Greenwich Castle was chosen by Sir Christopher Wren, a former Savilian Professor of Astronomy; as Greenwi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
