statefeed1
\documentclass{standalone} \usepackage{tikz} \usetikzlibrary{shapes,positioning,calc} \usetikzlibrary{narrow} % The double arrow comes from % http://www.texample.net/tikz/examples/double-arrows/ % with modification in % http://tex.stackexchange.com/questions/169061/tikz-increase-arrow-head-size \usetikzlibrary{arrows,decorations.markings} \tikzset{every picture/.style={auto, line width=1pt, >=narrow, x=1mm, y=1mm, font=\small}} \tikzset{block/.style={draw, rectangle, line width=2pt, fill=blue!10, minimum height=3em, minimum width=3em, outer sep=0pt}} \tikzset{sumcircle/.style={draw, circle, outer sep=0pt, label=center:{{\Large$\Sigma$}}, minimum width=2em}} \tikzset{vecArrow/.style={ line width=1pt, decoration={ markings,mark=at position 1 with { \arrow[scale=2.5,line width=0.4pt] {open triangle 60} } }, double distance=4pt, shorten >= 13pt, preaction = {decorate}, postaction = {draw,line width=4pt, white,shorten >= 10pt} }} \tikzset{innerWhite/.style={semithick, white, line width=1.4pt, shorten >= 4.5pt}} \begin{document} \begin{tikzpicture} \node[sumcircle](sumA){}; \node[block, right=25mm of sumA](Adam){Adam}; \node[block,below=8mm of sumA,xshift=15mm](Bertil){Bertil}; \node[block,left=10mm of sumA](Cesar){Cesar}; \draw[->](Cesar.west)++(-15,0)--node[xshift=-2mm]{$AA$}(Cesar); \draw[->](Cesar)--(sumA); \draw[->](sumA)--node{$BB$}(Adam); \draw[->](Adam.east)--node{$CC$}+(15,0); \draw[vecArrow](Adam)|-(Bertil); \draw[->](Bertil)-|(sumA); \end{tikzpicture} \end{document}