What does an analog signal represent in control systems?

An analog signal represents a continuous signal that varies over time, which is fundamental in control systems. Unlike digital signals that represent discrete values and are typically limited to specific states (such as on/off), analog signals can represent a continuum of values. This characteristic of analog signals allows them to accurately depict real-world phenomena, such as temperature, pressure, or flow, which change smoothly rather than in distinct steps.

In a control system, using analog signals enables the representation of variables that need to be monitored and controlled in real-time. For instance, a temperature sensor might output a voltage that varies proportionally to the temperature it senses, providing precise feedback for control actions.

The other options do not accurately describe analog signals. The first option refers to discrete signals, which do not capture the continuous nature of analog signals. The third option describes fixed numbers that would apply more to digital systems, where binary conditions are represented as high or low states. Finally, the last option suggests a limitation to digital communication, whereas analog signals are widely used in various applications beyond digital contexts.