Das hier sollte passen. Alles Weitere klärt dann die Anleitung von »
PGF/TikZ«.
\documentclass[11pt,a4paper,ngerman]{article}
\usepackage[T1]{fontenc}
\usepackage{selinput}
\SelectInputMappings{
adieresis={ä},
germandbls={ß}
}
\usepackage{babel}
\usepackage{tikz}
\usepackage{lmodern}
\usepackage{microtype}
\begin{document}
\begin{tikzpicture}[>=stealth,thick]
% \draw[help lines] (-4,-2) grid (6,2);
\draw[double,double distance=3pt] (-0.2,0) -- (0.2,0);
\node[draw,minimum width=3em,minimum height=2em] (PI) at (-2,0) {PI};
\node[draw,minimum width=3em,minimum height=2em] (P) at (3,1) {P};
\node[draw,minimum width=3em,minimum height=2em] (I) at (3,-1) {I};
\node[draw,circle] (0) at (4.5,0) {};
\draw[->] (-4,0) -- (PI) node[midway,above] {$e(t)$};
\draw[->] (PI) -- (-0.5,0) node[midway,above] {$y(t)$};
\draw[->] (0.5,0) --(1.5,0) node[midway,above] {$e(t)$};
\draw (P) -- +(-1.5,0) |- (I);
\draw[->] (P) -| (0);
\draw[->] (I) -| (0);
\draw[->] (0) -- +(1.5,0) node [midway,above] {$y(t)$};
\end{tikzpicture}
\end{document}