Closed-loop transfer function

In telecommunication, a closed-loop transfer function 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.

Note 1: The closed-loop transfer function is measured at the output.

Note 2: The output signal waveform can be calculated from the closed-loop transfer function and the input signal waveform.

Source: from Federal Standard 1037C