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A closed-loop control system is stable if the Nyquist plot of the corresponding open-loop transfer function

- encircles the $s$-plane point $(-1+j0)$ in the counter clockwise direction as many times as the number of right-half $s$-plane poles.
- encircles the $s$-plane point $(0-j1)$ in the clockwise direction as many times as the number of right- half $s$-plane poles.
- encircles the $s$-plane point $(-1+j0)$ in the counterclockwise direction as many times as the number of left-half-$s$-plane poles.
- encircles the $s$-plane point $(-1+j0)$ in the counterclockwise direction as many times as the number of right-half $s$-plane zeroes.