\begin{tikzpicture}[->, >=stealth, shorten >= 0pt, draw=black!50, node distance=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, text width = 1cm, align= center] (H1) {$H_1(z)$};
    \node[block, right of=H1, text width = 1cm, align= center] (M1) {$~~M_1$};
    \draw[-latex, shorten >= 15pt, shorten <= 15pt, line width=0.75pt] ($(M1.north)-(7pt, 0)$) -- ($(M1.south)-(7pt, 0)$) {};
   	\node[block, right=1cm of M1, text width = 1cm, align= center] (H2) {$H_2(z)$};
    \node[block, right of=H2, text width = 1cm, align= center] (M2) {$~~M_2$};
    \draw[-latex, shorten >= 15pt, shorten <= 15pt, line width=0.75pt] ($(M2.north)-(7pt, 0)$) -- ($(M2.south)-(7pt, 0)$) {};
	\coordinate (yc) at ($(M2.east)+(1cm, 0)$) {};
		
    \path (xc) edge (H1);
    \path (H1) edge (M1);
    \path (M1) edge (H2);
    \path (H2) edge (M2);
    \path (M2) edge (yc);
    
    \node[above = 0mm of xc, text width = 1cm, align=center] {$x[n]$};
    \node[above = 0mm of yc, text width = 1cm, align=center] {$y[n]$};
    \draw[dashed] ($(H1.south west)-(0.3cm, 0.4cm)$) rectangle ($(M1.north east)+(0.3cm, 0.4cm)$) {};
    \node[align=center] at ($(H1.west)!0.5!(M1.east) - (0, 1.5cm)$) {Decimator 1};
    \draw[dashed] ($(H2.south west)-(0.3cm, 0.4cm)$) rectangle ($(M2.north east)+(0.3cm, 0.4cm)$) {};
    \node[align=center] at ($(H2.west)!0.5!(M2.east) - (0, 1.5cm)$) {Decimator 2};
\end{tikzpicture}