\documentclass[tikz]{standalone}

\usetikzlibrary{shapes.geometric, arrows}
\tikzstyle{dspsquare}=[rectangle, thick, draw=black, fill=gray!10, minimum size=1cm]
\tikzstyle{dspcircle}=[circle, thick, draw=black, fill=gray!10, minimum size=1cm]
\tikzstyle{dsptriangle}=[isosceles triangle, thick, draw=black, fill=gray!10, minimum size=1cm]
\tikzstyle{dspjoint}=[fill, draw=black, shape=circle, minimum size=3pt, inner sep=0]
\tikzstyle{dspio}=[draw=black, shape=circle, minimum size=5pt, inner sep=0]



\begin{document}

\begin{tikzpicture}[>=triangle 45]
\matrix(m1) [row sep=5mm, column sep=5mm]
{
    \node[dspio, label=left:$x(n)$]             (m00)   {};                     &
    \node[dspjoint]                             (m01)   {};                     &
    \node[dsptriangle]                          (m02)   {$b_0$};                &
    \node                                       (m03)   {};                     &
    \node[dspcircle]                            (m04)   {$+$};                  &
    \node[dspio, label=right:$y(n)$]            (m05)   {};                     \\
    %------------------------------------------------------------------------------
    \node                                       (m10)   {};                     &
    \node[dspsquare]                            (m11)   {$z^{-1}$};             &
    \node                                       (m12)   {};                     &
    \node                                       (m13)   {};                     &
    \node                                       (m14)   {};                     &
    \node                                       (m15)   {};                     \\
    %------------------------------------------------------------------------------
    \node                                       (m20)   {};                     &
    \node[dspjoint]                             (m21)   {};                     &
    \node[dsptriangle]                          (m22)   {$b_1$};                &
    \node                                       (m23)   {};                     &
    \node                                       (m24)   {};                     &
    \node                                       (m25)   {};                     \\
    %------------------------------------------------------------------------------
    \node                                       (m30)   {};                     &
    \node[dspsquare]                            (m31)   {$z^{-1}$};             &
    \node                                       (m32)   {};                     &
    \node                                       (m33)   {};                     &
    \node                                       (m34)   {};                     &
    \node                                       (m35)   {};                     \\
    %------------------------------------------------------------------------------
    \node                                       (m40)   {};                     &
    \node[dspjoint]                             (m41)   {};                     &
    \node[dsptriangle]                          (m42)   {$b_2$};                &
    \node                                       (m43)   {};                     &
    \node                                       (m44)   {};                     &
    \node                                       (m45)   {};                     \\
    %------------------------------------------------------------------------------
    \node                                       (m50)   {};                     &
    \node                                       (m51)   {};                     &
    \node                                       (m52)   {};                     &
    \node                                       (m53)   {};                     &
    \node                                       (m54)   {};                     &
    \node                                       (m55)   {};                     \\
    %------------------------------------------------------------------------------
    \node                                       (m60)   {};                     &
    \node[dspsquare]                            (m61)   {$z^{-1}$};             &
    \node                                       (m62)   {};                     &
    \node                                       (m33)   {};                     &
    \node                                       (m64)   {};                     &
    \node                                       (m65)   {};                     \\
    %------------------------------------------------------------------------------
    \node                                       (m70)   {};                     &
    \node                                       (m71)   {};                     &
    \node[dsptriangle]                          (m72)   {$b_N$};                &
    \node                                       (m73)   {};                     &
    \node                                       (m74)   {};                     &
    \node                                       (m75)   {};                     \\
    %------------------------------------------------------------------------------
};

\draw[->]   (m00) -- (m02);
\draw[->]   (m02) -- (m04);
\draw[-]    (m04) -- (m05);
\draw[->]   (m01) -- (m11);
\draw[->]   (m11) -- (m31);
\draw[->]   (m21) -- (m22);
\draw[-]    (m31) -- (m41);
\draw[->]   (m41) -- (m42);
\draw[->, densely dashed]   (m41) -- (m61);
\draw[->]   (m61) |- (m72);

\draw[->]   (m22) -- (m23.west) -- (m04);
\draw[->]   (m42) -- (m43.west) -- (m04);
\draw[->]   (m72) -- (m73.west) -- (m04);
\end{tikzpicture}

\end{document}