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

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

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. Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio ...

), 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 synchrono ...

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 systems, complex dynamical systems, usually by employing differential equations by nature of the ergodic theory, ergodicity of dynamic systems. When differ ...

, an

oscillator Oscillation is the repetitive or periodic variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. Familiar examples of oscillation include a swinging pendulum ...

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 Chronometry or horology () is the science studying the measurement of time and timekeeping. Chronometry enables the establishment of standard measurements of time, which have applications in a broad range of social and scientific areas. ''Hor ...

, a mechanical

clock A clock or chronometer is a device that measures and displays time. The clock is one of the oldest Invention, human inventions, meeting the need to measure intervals of time shorter than the natural units such as the day, the lunar month, a ...

watch A watch is a timepiece carried or worn by a person. It is designed to maintain a consistent movement despite the motions caused by the person's activities. A wristwatch is worn around the wrist, attached by a watch strap or another type of ...

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

devices. Simply put, if a power providing device (e.g. a spring or weight) provides constant torque to the wheel train, it will be isochronous, since the

escapement An escapement is a mechanical linkage in mechanical watches and clocks that gives impulses to the timekeeping element and periodically releases the gear train to move forward, advancing the clock's hands. The impulse action transfers energy to t ...

will experience the same force regardless of how far the weight has dropped or the spring has unwound. *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

telecommunications Telecommunication, often used in its plural form or abbreviated as telecom, is the transmission of information over a distance using electronic means, typically through cables, radio waves, or other communication technologies. These means of ...

, an

isochronous signal In telecommunications, an isochronous signal is a signal in which the time interval separating any two significant instants is equal to the unit interval or a multiple of the unit interval. Variations in the time intervals are constrained within ...

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 analysi ...

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

data transmission Data communication, including data transmission and data reception, is the transfer of data, signal transmission, transmitted and received over a Point-to-point (telecommunications), point-to-point or point-to-multipoint communication chann ...

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 mathematica ...

relationship. ** Isochronous burst transmission 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, developed by USB Implementers Forum (USB-IF), for digital data transmission and power delivery between many types of electronics. It specifies the architecture, in particular the physical ...

used in

computer A computer is a machine that can be Computer programming, programmed to automatically Execution (computing), carry out sequences of arithmetic or logical operations (''computation''). Modern digital electronic computers can perform generic set ...

s, ''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 a ...

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 electric charge, charged particles to very high speeds and energies to contain them in well-defined particle beam, beams. Small accelerators are used for fundamental ...

s an

isochronous cyclotron A cyclotron is a type of particle accelerator invented by Ernest 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: January ...

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, isoquant or isarithm) of a Function of several real variables, 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 ...

of equal time, for instance, in geological layers, tree rings or

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 freq ...

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 wikt:isochrone, isochrone (iso = equal, chrone = time) is defined as "a line drawn on a map connecting poi ...

or diagram shows such contours. *In

linguistics Linguistics is the scientific study of language. The areas of linguistic analysis are syntax (rules governing the structure of sentences), semantics (meaning), Morphology (linguistics), morphology (structure of words), phonetics (speech sounds ...

isochrony Isochrony is a linguistic analysis or hypothesis assuming that any spoken language's utterances are divisible into equal rhythmic portions of some kind. Under this assumption, languages are proposed to broadly fall into one of two categories based ...

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

neurology Neurology (from , "string, nerve" and the suffix wikt:-logia, -logia, "study of") is the branch of specialty (medicine) , medicine dealing with the diagnosis and treatment of all categories of conditions and disease involving the nervous syst ...

, isochronic tones are regular beats of a single

tone Tone may refer to: Visual arts and color-related * Tone (color theory), a mix of tint and shade, in painting and color theory * Tone (color), the lightness or brightness (as well as darkness) of a color * Toning (coin), color change in coins * ...

used for brainwave entrainment.

References

{{Reflist Synchronization Telecommunication theory Horology

See also

References