A signal can be used to control the speed of a motor, determine the position of a valve, or indicate the level of a tank as it fills. What type of signal is this?

• A. Digital
• B. Analog
• C. Pulse
• D. Hybrid

Answer: (B)

The key idea is proportional, continuous control. When you want to control something like motor speed, valve position, or a tank level, you need a signal that can take a range of values, not just on/off. An analog signal fits this because it changes smoothly in amplitude or current, allowing any intermediate value to be commanded. For example, a motor can be commanded with a 0–10 V (or 4–20 mA) analog signal to set any speed, a valve can move to any intermediate position based on the same kind of signal, and a level indicator can reflect the exact current level as the tank fills.

In contrast, digital signals switch between discrete states (high or low), which is great for binary decisions but not for proportional control without additional processing. A pulse signal is a specific on/off waveform used for timing or pulse-width modulation, which still represents information in a binary manner rather than a continuous range. A hybrid signal would combine aspects of both but isn’t necessary for the scenario described.

So the description matches an analog signal.