The open loop transfer function of a unity feedback control system is given by

$G(s)=\frac{k(s+1)}{s(1+Ts)(1+2S)'}, K > 0, T > 0.$

The closed loop system will be stable if

- $0 < T < \frac{4(K+1)}{K-1}$
- $0 < K < \frac{4(T+2)}{T-2}$
- $0 < K < \frac{T+2}{T-2}$
- $0 < T < \frac{8(k+1)}{K-1}$