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Arrangement whereby a company employs only workers who are members in good standing of a specified labour union. It is the most rigid of the various schemes for protecting labour unions (more flexible arrangements include the union shop). Closed shops were declared illegal in the U.S. under the Taft-Hartley Act of 1947, but in practice they continue to exist in some industries, such as construction.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.

A closed-loop transfer function in control theory is a mathematical expression (algorithm) describing the net result of the effects of a closed (feedback) loop on the input signal to the circuits enclosed by the loop.
## Overview

The closed-loop transfer function is measured at the output. The output signal waveform can be calculated from the closed-loop transfer function and the input signal waveform.## Derivation

Let's define an intermediate signal Z shown as follows:## See also

## References

An example of a closed-loop transfer function is shown below:

The summing node and the G(s) and H(s) blocks can all be combined into one block, which would have the following transfer function:

- $dfrac\{Y(s)\}\{X(s)\}\; =\; dfrac\{G(s)\}\{1\; +\; G(s)\; H(s)\}$

Using this figure we can write

- $Y(s)\; =\; Z(s)G(s)\; Rightarrow\; Z(s)\; =\; dfrac\{Y(s)\}\{G(s)\}$

- $X(s)-Y(s)H(s)\; =\; Z(s)\; =\; dfrac\{Y(s)\}\{G(s)\}\; Rightarrow\; X(s)\; =\; Y(s)\; left[\{1+G(s)H(s)\}\; right]/G(s)$

- $Rightarrow\; dfrac\{Y(s)\}\{X(s)\}\; =\; dfrac\{G(s)\}\{1\; +\; G(s)\; H(s)\}$

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Last updated on Thursday May 08, 2008 at 05:02:41 PDT (GMT -0700)

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This article is licensed under the GNU Free Documentation License.

Last updated on Thursday May 08, 2008 at 05:02:41 PDT (GMT -0700)

View this article at Wikipedia.org - Edit this article at Wikipedia.org - Donate to the Wikimedia Foundation

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