\psset{xunit=1cm, yunit=1cm}
%\psframebox{
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\begin{pspicture}(-0.5,-0.5)(6.5,3.1)
%\psgrid(0,0)(7,3.5)

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\pspolygon[linewidth=0.4pt,fillstyle=solid](4.5,-0.2)(5.5,-0.2)(5.5,0.2)(4.5,0.2)
\pspolygon[linewidth=0.4pt,fillstyle=solid](2.8,2)(3.2,2)(3.2,1)(2.8,1)%0.4
\rput[c](1,0.5){$R_3$}
\rput[c](3.3,0.5){$I_2$}
\rput[c](3.7,-0.3){$I_1$}
\rput[c](5,0.5){$R_1$}
\rput[c](3.5,1.5){$R_2$}
\rput[c](6.3,1.5){$U_2$}
\rput[c](-0.3,1.5){$U_1$}
\rput[c](3,-0.3){$A$}
\rput[c](2.3,-0.3){$I_3$}
\pscircle[linewidth=0.4pt](4.5,1.5){0.3}
\rput[c](4.5,1.5){II}
\pscircle[linewidth=0.4pt](1.5,1.5){0.3}
\rput[c](1.5,1.5){I}
\psline[linewidth=0.2pt,arrowsize=1.5mm,arrowlength=1.5,arrowinset=0.3]{<-}(2.2,0)(2.4,0)
\psline[linewidth=0.2pt,arrowsize=1.5mm,arrowlength=1.5,arrowinset=0.3]{<-}(3.6,0)(3.8,0)
\psline[linewidth=0.2pt,arrowsize=1.5mm,arrowlength=1.5,arrowinset=0.3]{->}(3,0.6)(3,0.4)
\psline[linewidth=0.3pt,linestyle=dashed, arrowsize=1.5mm,arrowlength=1.5,arrowinset=0.3]{->}(0,2.8)(0,0.2)
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\psline[linewidth=0.2pt](1.5,0)(4.5,0)
\psline[linewidth=0.2pt]{-o}(5.5,0)(6,0)%0.2
\psline[linewidth=0.2pt]{o-o}(0,3)(6,3)%0.2
\psline[linewidth=0.2pt]{o-}(0,0)(0.5,0)%0.2
\psline[linewidth=0.2pt](3,0)(3,1)
\psline[linewidth=0.2pt](3,2)(3,3)
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\pscircle[linewidth=0.2pt,fillstyle=solid, fillcolor=black ](3,3){0.035}
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%%http://sites.inka.de/picasso/latex.html


%ticks=none,labels=none]{->}(