Explanation: Unlike the backward difference method, the left-half s-plane is now mapped entirely inside the unit circle, |z|=1, rather than to a part of it. Also, the imaginary axis is mapped to the unit circle. Therefore, equation s = \\(\\frac{2}{T}[\\frac{1-z^{-1}}{1+z^{-1}}]\\) is a true frequency-to-frequency transformation.