Consider a feedback control system with loop transfer function $$$G\left(s\right)H\left(s\right)=\frac{K\left(1+0.5s\right)}{s\left(1+s\right)\left(1+2s\right)}$$$ The type of the closed loop system is

In figure, A = 1 and B = 1. The input B is now replaced by a sequence 101010 ___, the outputs x and y will be

The noise margin of a TTL gate is about

The threshold voltage for each transistor in Fig.2.5, is 2V. For this circuit to work as an inverter, Vi must take the values