CONTROL LOOP DIAGRAMS Process ControlsFigure 5 Block and ArrowsAlthough blocks are used to identify many types of mathematical operations, operations ofaddition and subtraction are represented by a circle, called a summing point. As shown in Figure6, a summing point may have one or several inputs. Each input has its own appropriate plus orminus sign. A summing point has only one output and is equal to the algebraic sum of theinputs.Figure 6 Summing PointsA takeoff point is used to allow a signal to be used by more than one block or summing point(Figure 7).IC-07 Page 8 Rev. 0

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