Block Diagram Reduction Rules.Step 1 − Use Rule 1 for blocks $G_1$and $G_2$. Use Rule 2 for blocks $G_3$and $G_4$. The modified block diagram is shown in the following figure.Step 2 − Use Rule 3 for blocks $G_1G_2$and $H_1$. Use Rule 4 for shifting take-off point after the block $G_5$. The modified block diagram isStep 3 − Use Rule 1 for blocks $(G_3 +G_4)$and $G_5$. The modified block diagram is shown in the following figure.Step 4 − Use Rule 3 for blocks $(G_3 +G_4)G_5$and $H_3$. The modified block diagram is shown in the following figure.More items Control Systems - Block Diagram Reduction - Tutorialspoint Was this helpful? Wescott Design Services: Using Block Diagrams 1 The Language of Blocks. What is specified in this block diagram is a single input signal, a single output signal, and the dependence of the output signal on the input signal and it's past values, and possibly on the initial conditions of the block ï¿½Thingï¿½ at some specified point in time.