In Figure 1.6, the setpoint (SP) is the input to the process control system, and the controlled variable (C) is the output. The feedback path consists of one component, the measuring transmitter with transfer function H. The forward path consists of three components (the control modes, the manipulating element, and the process) with transfer functions , , and , respectively. The overall forward transfer function (G) is the product of the three component transfer functions: G =