A sequence of events is isochronous if the events occur regularly, or at equal

time Time is the continued sequence of existence and events that occurs in an apparently irreversible succession from the past, through the present, into the future. It is a component quantity of various measurements used to sequence events, ...

intervals. The term ''isochronous'' is used in several technical contexts, but usually refers to the primary subject maintaining a constant period or interval (the reciprocal of

frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...

), despite variations in other measurable factors in the same system. Isochronous timing is a characteristic of a repeating event whereas

synchronous Synchronization is the coordination of events to operate a system in unison. For example, the conductor of an orchestra keeps the orchestra synchronized or ''in time''. Systems that operate with all parts in synchrony are said to be synchronou ...

timing refers to the relationship between two or more events. *In

dynamical systems theory Dynamical systems theory is an area of mathematics used to describe the behavior of complex dynamical systems, usually by employing differential equations or difference equations. When differential equations are employed, the theory is called '' ...

, an oscillator is called ''isochronous'' if its

is independent of its

amplitude The amplitude of a periodic variable is a measure of its change in a single period (such as time or spatial period). The amplitude of a non-periodic signal is its magnitude compared with a reference value. There are various definitions of am ...

. *In

horology Horology (; related to Latin '; ; , interfix ''-o-'', and suffix ''-logy''), . is the study of the measurement of time. Clocks, watches, clockwork, sundials, hourglasses, clepsydras, timers, time recorders, marine chronometers, and atomic clo ...

, a mechanical

clock A clock or a timepiece is a device used to measure 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 such as the day, the lunar month and t ...

watch A watch is a portable timepiece intended to be carried or worn by a person. It is designed to keep a consistent movement despite the motions caused by the person's activities. A wristwatch is designed to be worn around the wrist, attached b ...

is ''isochronous'' if it runs at the same rate regardless of changes in its drive force, so that it keeps correct time as its

mainspring A mainspring is a spiral torsion spring of metal ribbon—commonly spring steel—used as a power source in mechanical watches, some clocks, and other clockwork mechanisms. ''Winding'' the timepiece, by turning a knob or key, stores energy in ...

unwinds or chain length varies. Isochrony is important in

timekeeping Time is the continued sequence of existence and events that occurs in an apparently irreversible succession from the past, through the present, into the future. It is a component quantity of various measurements used to sequence events, to ...

devices. Simply put, if a power providing device (ie a spring or weight) provides constant torque to the wheel train, it is isochronous (since springs provide weaker power the less pressure is applied it isn't isochronous, but since gravity's force on a mass is constant then it is isochronous). *In electrical power generation, ''isochronous'' means that the frequency of the electricity generated is constant under varying load; there is zero generator droop. (See

Synchronization (alternating current) In an alternating current electric power system, synchronization is the process of matching the frequency of a generator or other source to a running network. An AC generator cannot deliver power to an electrical grid unless it is running at the sam ...

.) *In

telecommunications Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...

, an

isochronous signal In telecommunication, an isochronous signal is a signal in which the time interval separating any two significant instants is equal to the unit interval In mathematics, the unit interval is the closed interval , that is, the set of all real n ...

is one where the

interval separating any two corresponding transitions is equal to the

unit interval In mathematics, the unit interval is the closed interval , that is, the set of all real numbers that are greater than or equal to 0 and less than or equal to 1. It is often denoted ' (capital letter ). In addition to its role in real analysis ...

or to a multiple of the unit interval; but phase is arbitrary and potentially varying. **The term is also used in

data transmission Data transmission and data reception or, more broadly, data communication or digital communications is the transfer and reception of data in the form of a digital bitstream or a digitized analog signal transmitted over a point-to-point o ...

to describe cases in which corresponding significant instants of two or more sequential signals have a constant

phase Phase or phases may refer to: Science *State of matter, or phase, one of the distinct forms in which matter can exist *Phase (matter), a region of space throughout which all physical properties are essentially uniform * Phase space, a mathematic ...

relationship. **

Isochronous burst transmission Isochronous burst transmission is a method of transmission. In a data network where the information-bearer channel rate is higher than the input data signaling rate, transmission is performed by interrupting, at controlled intervals, the data st ...

is used when the information-bearer channel rate is higher than the input data signaling rate. *In the

Universal Serial Bus Universal Serial Bus (USB) is an industry standard that establishes specifications for cables, connectors and protocols for connection, communication and power supply (interfacing) between computers, peripherals and other computers. A broad ...

used in computers, ''isochronous'' is one of the four data flow types for USB devices (the others being Control, Interrupt and Bulk). It is commonly used for streaming data types such as video or audio sources. Similarly, the

IEEE 1394 interface IEEE 1394 is an interface standard for a serial bus for high-speed communications and isochronous real-time data transfer. It was developed in the late 1980s and early 1990s by Apple in cooperation with a number of companies, primarily Sony an ...

standard, commonly called Firewire, includes support for isochronous streams of audio and video at known constant rates. *In

particle accelerator A particle accelerator is a machine that uses electromagnetic fields to propel charged particles to very high speeds and energies, and to contain them in well-defined beams. Large accelerators are used for fundamental research in particle ...

s an

isochronous cyclotron A cyclotron is a type of particle accelerator invented by Ernest O. Lawrence in 1929–1930 at the University of California, Berkeley, and patented in 1932. Lawrence, Ernest O. ''Method and apparatus for the acceleration of ions'', filed: Janu ...

is a cyclotron where the field strength increases with radius to compensate for relativistic increase in mass with speed. *An isochrone is a

contour line A contour line (also isoline, isopleth, or isarithm) of a function of two variables is a curve along which the function has a constant value, so that the curve joins points of equal value. It is a plane section of the three-dimensional grap ...

of equal time, for instance, in geological layers,

tree rings Dendrochronology (or tree-ring dating) is the scientific method of dating tree rings (also called growth rings) to the exact year they were formed. As well as dating them, this can give data for dendroclimatology, the study of climate and atmos ...

wave front In physics, the wavefront of a time-varying ''wave field'' is the set (locus) of all points having the same '' phase''. The term is generally meaningful only for fields that, at each point, vary sinusoidally in time with a single temporal frequ ...

s. An

isochrone map An isochrone map in geography and urban planning is a map that depicts the area accessible from a point within a certain time threshold. An isochrone (iso = equal, chrone = time) is defined as "a line drawn on a map connecting points at which som ...

or diagram shows such contours. *In

linguistics Linguistics is the science, scientific study of human language. It is called a scientific study because it entails a comprehensive, systematic, objective, and precise analysis of all aspects of language, particularly its nature and structure ...

isochrony Isochrony is the postulated rhythmic division of time into equal portions by a language. Rhythm is an aspect of prosody, others being intonation, stress, and tempo of speech. Three alternative ways in which a language can divide time are postula ...

is the postulated rhythmic division of time into equal portions by a language. *In

neurology Neurology (from el, νεῦρον (neûron), "string, nerve" and the suffix -logia, "study of") is the branch of medicine dealing with the diagnosis and treatment of all categories of conditions and disease involving the brain, the spinal ...

, isochronic tones are regular beats of a single tone used for

brainwave entrainment Brainwave entrainment, also referred to as brainwave synchronization or neural entrainment, refers to the observation that brainwaves (large-scale electrical oscillations in the brain) will naturally synchronize to the rhythm of periodic externa ...

References

{{Reflist Synchronization Telecommunication theory Horology

See also

References