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A time-invariant (TIV) system is a system whose output does not depend explicitly on time. Such systems are regarded as a class of systems in the field of system analysis. Lack of time dependence is captured in the following mathematical property of such a system: :''If the input signal produces an output then any time shifted input, , results in a time-shifted output '' This property can be satisfied if the transfer function of the system is not a function of time except expressed by the input and output. In the context of a system schematic, this property can also be stated as follows: :''If a system is time-invariant then the system block commutes with an arbitrary delay.'' If a time-invariant system is also linear, it is the subject of LTI system theory (linear time-invariant) with direct applications in NMR spectroscopy, seismology, circuits, signal processing, control theory, and other technical areas. Nonlinear time-invariant systems lack a comprehensive, governing theory. Discrete time-invariant systems are known as shift-invariant systems. Systems which lack the time-invariant property are studied as time-variant systems. == Simple example == To demonstrate how to determine if a system is time-invariant, consider the two systems: * System A: * System B: Since system A explicitly depends on ''t'' outside of and , it is not time-invariant. System B, however, does not depend explicitly on ''t'' so it is time-invariant. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Time-invariant system」の詳細全文を読む スポンサード リンク
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