\unitlength0.2mm
\begin{picture}(640,400)
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\put(  70, 260){\framebox( 180,  30){Instruction counter}}
\put( 300, 320){\framebox( 120,  50){Control logic}}
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\put( 290,0){\framebox( 140, 220){Vector generator}}
\put( 450, 180){\framebox( 160,  40){X deflection driver}}
\put( 450,0){\framebox( 160,  40){Y deflection driver}}
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\put(  10, 415){to computer}
\put(  10, 385){from computer}
\put( 440, 115){Beam}
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\put( 205, 245){+1}
\put( 410, 390){\framebox( 200,  40){Display Processing Unit}}
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\end{picture}
