Synchronization or synchronisation^[1] is timekeeping which requires the coordination of events to operate a system in unison. A timekeeper is an instrument or person that measures the passage of Time; in the case of the latter often with the assistance of a Clock or Stopwatch. System (from Latin systēma, in turn from Greek systēma is a set of interacting or interdependent Entities, real or abstract The familiar conductor of an orchestra serves to keep the orchestra in time. Conducting is the act of directing a Musical performance by way of visible gestures Systems operating with all their parts in synchrony are said to be synchronous or in sync. Some systems may be only approximately synchronized, or plesiochronous. The term Plesiochronous is derived from the Greek plesio, meaning near and chronos, time and refers to the fact that plesiochronous systems run in a state where For some applications relative offsets between events need to be determined, for others only the order of the event is important.

Today, synchronization can occur on a global basis due to GPS-enabled timekeeping systems. Basic concept of GPS operation A GPS receiver calculates its position by carefully timing the signals sent by the constellation of GPS Satellites high above the Earth

Transport

Apart from its use for navigation (see John Harrison), synchronization was not important in transportation until the nineteenth century, when the coming of the railways made travel fast enough for the differences in local time between adjacent towns to be noticeable (see [1]). John Harrison (24 March 1693 – 24 March 1776 was an English Clockmaker.

In some territories, sharing of single railroad tracks was controlled by the timetable. Thus strict timekeeping was a safety requirement. To this day, railroads can communicate and signal along their tracks, independently of other systems for safety.

Communication

The lessons of timekeeping are part of engineering technology. In electrical engineering terms, for digital logic and data transfer, a synchronous object requires a clock signal. Electrical engineering, sometimes referred to as electrical and electronic engineering, is a field of Engineering that deals with the study and application of In Electronics and especially synchronous Digital circuits a clock signal is a signal used to coordinate the actions of two or more circuits

Timekeeping technologies such as the GPS satellites and Network time protocol (NTP) provide real-time access to a close approximation to the UTC timescale, and are used for many terrestrial synchronization applications. Basic concept of GPS operation A GPS receiver calculates its position by carefully timing the signals sent by the constellation of GPS Satellites high above the Earth The Network Time Protocol ( NTP) is a protocol for distributing the Coordinated Universal Time (UTC by means of synchronizing the clocks of computer systems

Synchronization is an important concept in the following fields:

• Computer science "In computer science, especially parallel computing, synchronization means the coordination of simultaneous threads or processes to complete a task in order to get correct runtime order and avoid unexpected race conditions. In Computer science, synchronization refers to one of two distinct but related concepts synchronization of processes, and synchronization of data "
• Telecommunication
• Physics The idea of simultaneity has many difficulties, both in practice and theory. Physics (Greek Physis - φύσις in everyday terms is the Science of Matter and its motion.
• Cryptography
• Multimedia
• Photography
• Music (rhythm)
• Synthesizers

Synchronization has several subtly distinct sub-concepts:

• Rate synchronization
• Phase synchronization
• Time offset synchronization
• Time order synchronization

Some uses of synchronization

While well-designed time synchronization is an important tool for creating reliable systems, excessive use of synchronization where it is not necessary can make systems less fault-tolerant, and hence less reliable. Cryptography (or cryptology; from Greek grc κρυπτός kryptos, "hidden secret" and grc γράφω gráphō, "I write" Multimedia is media and content that utilizes a combination of different content forms. Photography (fә'tɒgrәfi or fә'tɑːgrәfi (from Greek φωτο and γραφία is the process and Art of recording pictures by means of capturing Music is an Art form in which the medium is Sound organized in Time. Rhythm (from Greek ῥυθμός - rhythmos, "any measured flow or movement symmetry" is the variation of the length and accentuation of Oscillator sync is a feature in Synthesizers One Oscillator will restart the period of another oscillator so that they will have the same base frequency Phase synchronization is the process by which two or more cyclic signals tend to oscillate with a repeating sequence of relative phase angles

• Film synchronization of image and sound in sound film. An image (from Latin imago) or picture is an artifact usually two-dimensional that has a similar appearance to some subject &mdashusually Sound' is Vibration transmitted through a Solid, Liquid, or Gas; particularly sound means those vibrations composed of Frequencies A sound film is a motion picture with synchronized sound, or sound technologically coupled to image as opposed to a Silent film.
• Synchronization is important in fields such as digital telephony, video and digital audio where streams of sampled data are manipulated. Digital telephony is the use of digital electronics in the provision of digital Telephone services and systems Video is the technology of electronically capturing, Recording, processing storing transmitting and reconstructing a sequence of Still images Digital audio uses Digital signals for Sound reproduction. This includes analog-to-digital conversion, digital-to-analog conversion, storage
• Arbiters are needed in digital electronic systems such as microprocessors to deal with asynchronous inputs. Arbiters are electronic devices that allocate access to shared resources A microprocessor incorporates most or all of the functions of a Central processing unit (CPU on a single Integrated There are also electronic digital circuits called synchronizers that attempt to perform arbitration in one clock cycle. Synchronizers, unlike arbiters, are prone to failure. (See metastability in electronics). Metastability in electronics is the ability of a non-equilibrium electronic state to persist for a long (and theoretically unlimited period of time (see Asynchronous circuit
• Encryption systems usually require some synchronization mechanism to ensure that the receiving cipher is decoding the right bits at the right time.
• Automotive transmissions contain synchronizers which allow the toothed rotating parts (gears and splined shaft) to be brought to the same rotational velocity before engaging the teeth. A manual transmission (also known as a stick shift or just 'stick' 'straight drive' or standard transmission) is a type of transmission used in
• Synchronization is also important in industrial automation applications. Automation ( Ancient Greek: = self dictated) roboticization or industrial automation or Numerical control is the use of Control systems
• Time codes are often used as a means of synchronization in film, video, and audio applications. Video is the technology of electronically capturing, Recording, processing storing transmitting and reconstructing a sequence of Still images Sound' is Vibration transmitted through a Solid, Liquid, or Gas; particularly sound means those vibrations composed of Frequencies
• Flash photography, see Flash synchronization
• File synchronization is used to maintain the same version of files on multiple computing devices. A flash is a device used in Photography that produces an instantaneous flash of artificial Light Photography (fә'tɒgrәfi or fә'tɑːgrәfi (from Greek φωτο and γραφία is the process and Art of recording pictures by means of capturing In a Camera, flash synchronization is defined as the firing of a photographic flash coinciding with the shutter admitting light to Photographic File synchronization (or 'synching' or 'syncing' in computing is the process of making sure that two or more locations contain the same up-to-date files. For example, an address book on a telephone might need to be synchronized with an address book on a computer.
• Software applications must occasionally incorporate application-specific data synchronization in order to mirror changes over time among multiple data sources at a level more granular than File synchronization. Data synchronization is the process of establishing consistency among Data on remote sources and the continuous harmonization of the data over time File synchronization (or 'synching' or 'syncing' in computing is the process of making sure that two or more locations contain the same up-to-date files. An example use of this is the Data Synchronization specification of the Open Mobile Alliance, which continues the work previously done by the SyncML initiative. The Open Mobile Alliance ( OMA) is a Standards body which develops Open standards for the Mobile phone industry SyncML ( Synchronization Markup Language) is the former name (currently referred to as Open Mobile Alliance Data Synchronization and Device Management) SyncML was initially proposed to synchronize changes in personal address book and calendar information from computers to mobile phones, but has subsequently been used in applications that synchronize other types of data changes among multiple sources, such as project status changes. SyncML ( Synchronization Markup Language) is the former name (currently referred to as Open Mobile Alliance Data Synchronization and Device Management)
• The term synchronization is also sometimes used for the transfer of content from a computer to an MP3 player connected to it. MPEG-1 Audio Layer 3, more commonly referred to as MP3, is a Digital audio encoding format using a form of Lossy data compression

See also

• Asynchrony
• Clock synchronization
• Entrainment
• Flywheel
• Homochronous
• Mutual exclusion
• Phase-locked loops
• Reciprocal socialization
• Synchronism
• Synchronization (alternating current)
• Synchronization in telecommunications
• Synchronization of chaos
• Synchronizer
• Synchronous conferencing
• Time
• Time transfer
• Timecode

In the field of video and audio engineering:

• Genlock
• Jam sync
• Word sync

In the field of aircraft gun engineering:

• Interrupter gear

Order synchronization and related topics:

• Rendezvous problem
• Interlocking
• Race condition
• Concurrency control
• Room synchronization
• Transient blocking synchronization
• Comparison of synchronous and asynchronous signalling

Compare with:

• Synchronicity, a mystical notion due to Carl Jung. Asynchrony, in the general meaning is the state of not being synchronized. Clock synchronization is a problem from Computer science and Engineering which deals with the idea that internal Clocks of several computers may differ A flywheel is a mechanical device with significant Moment of inertia used as a storage device for Rotational energy. In Telecommunication, the term homochronous describes the relationship between two signals such that their corresponding significant instants are displaced by a constant Mutual exclusion (often abbreviated to mutex) Algorithms are used in Concurrent programming to avoid the simultaneous use of a common resource such as a A phase-locked loop or phase lock loop (PLL is a Control system that generates a signal that has a fixed relation to the phase of a "reference" Reciprocal socialization is a Socialization process that is bidirectional children socialize Parents just as parents socialize children Synchronization is an important concept in relation to Alternating current. Many services running on modern digital Telecommunications networks require accurate Synchronization for correct operation Synchronization of chaos is a phenomenon that may occur when two or more chaotic oscillators are coupled or when a chaotic oscillator drives another chaotic oscillator A manual transmission (also known as a stick shift or just 'stick' 'straight drive' or standard transmission) is a type of transmission used in Synchronous conferencing is the formal term used in Science, in particular in Computer-mediated communication, collaboration and learning, to For other uses see Time (disambiguation Time is a component of a measuring system used to sequence events to compare the durations of Time transfer describes methods for transferring reference clock Synchronization from one point to another often over long distances Genlock (for Gen erator Lock) is a common technique where the Video output of one source or a specific reference signal is used to synchronize Jam sync refers to the practice of applying a Phase hit to a system to bring it in Synchronization with another Word sync is a technique for synchronizing Digital audio signals between high-end professional devices such as CD players audio I/O cards etc Interrupter gear is a term that covers two related technologies The rendezvous dilemma is related to the Prisoner's dilemma and can be formulated in this way Two young people have a date in a park they have never been to In Railway signaling, an interlocking is an arrangement of signal apparatus that prevents conflicting movements through an arrangement of tracks such as junctions or crossings A race condition or race hazard is a flaw in a System or process whereby the output and/or result of the process is unexpectedly and critically dependent In Computer science, especially in the fields of Computer programming (see also Concurrent programming, Parallel programming) Operating systems The room synchronization technique is a form of Concurrency control in Computer science. Synchronous and asynchronous transmissions are two different methods of transmission synchronization Synchronicity is the Experience of two or more events which are causally unrelated occurring together in a meaningful manner

Notes

1. ^ see -ize vs -ise