a\begin{tikzpicture}[>=latex']
  \tikzset{block/.style= {draw, rectangle, align=center,minimum width=1.6cm,minimum height=1cm},
  }
  \node [coordinate]  (start) {};

  \node [coordinate, above = +6mm of start]  (src1) {};
  \node [coordinate, above = +2mm of start]  (src2) {};
  \node [coordinate, above = -2mm of start]  (src3) {};
  \node [coordinate, above = -6mm of start]  (src4) {};

  \node [coordinate, right = 16mm of src1] (inp1) {};
  \node [coordinate, right = 16mm of src2] (inp2) {};
  \node [coordinate, right = 16mm of src3] (inp3) {};
  \node [coordinate, right = 16mm of src4] (inp4) {};

  \node [coordinate] (inpc) at ($(inp1)!0.5!(inp4)$) {};

  \node [block, minimum height = 16mm, right = 00mm of inpc] (COMB){Combinator\\${\wrest}_{j\to i}$};        
  \node [block, right = 10mm of COMB] (INTG){Integrator\\${\crest}$, ${\Vbase}$, ${\Vreset}$};     
  \node [block, right = 10mm of INTG] (TRIG){Trigger\\${\Vmid}$, ${\Vdev}$}; 
  \node [coordinate, right = 2mm of TRIG] (FORK){}; 
  \node [coordinate, above = 10mm of FORK] (ELBOW){};        
  \node [coordinate, right = 8mm of FORK] (end){};

  \node [block, draw=red, right = -4mm of inpc, minimum height = 28mm, minimum width = 58mm] (BOX) {};

  \draw[->] (src1) -- (inp1);
  \draw[->] (src2) -- (inp2);
  \draw[->] (src3) -- (inp3);
  \draw[->] (src4) -- (inp4);

  \draw[->] (COMB) -- (INTG) node[above,pos=0.5] {$J$};
  \draw[->] (INTG) -- (TRIG) node[above,pos=0.5] {$V$};
  \draw[] (TRIG) -- (FORK);
  \draw[->] (FORK) -- (end) node[above,pos=0.5] {$X$};
  \draw[dashed,->] (FORK) -- (ELBOW) -| (INTG);
\end{tikzpicture}
