\begin{tikzpicture}[->, >=stealth, shorten >= 0pt, draw=black!50, node distance=3.2cm, font=\sffamily]
    \tikzstyle{node}=[circle,fill=black,minimum size=2pt,inner sep=0pt]
    \tikzstyle{block}=[draw=black,rectangle,fill=none,minimum size=1.5cm, inner sep=0pt]

	\node[node] (xc) {};
    \node[block, right=1cm of xc] (C) {$C(z)$};
    \node[block, right of=C] (P) {$H(z)$};
	\coordinate[right=1cm of P] (yc) {};
	
	\coordinate (mid1) at ($(P.east)!0.5!(C.west)$) {};
		
    \path (xc) edge (C);
    \path (C) edge (P);
    \path (P) edge (yc);
    
    \node[above = 0.5mm of mid1] {$x[n]$};
    \node[above = 0mm of xc, text width = 1cm, align=center] {$s[n]$};
    \node[above = 0mm of yc, text width = 1cm, align=center] {$y[n]$}; 
    \node[below] at ($(C.south)$) {Controller};
    \node[below] at ($(P.south)$) {Plant};
\end{tikzpicture}