For the signal constellation shown in the figure, the type of modulation is ________.

A binary source has symbol probabilities 0.8 and 0.2. If extension coding (blocks of 4 symbols) is used, the lower and upper bounds on the average code word length are :
(a)lower___________.
(b) higher_________.

Two resistors $$\,{R_1}$$ and $$\,{R_2}$$ (in ohms) at temperatures $${T_1}{}^ \circ K$$ and $${T_2}{}^ \circ K$$ respectively, are connected in series. Their equivalent noise temperature is.

In the signal flow graph of Figure, the gain c/r will be