The term that describes inputs and outputs that can have an infinite number of states is:

• A. Analog devices
• B. Discrete devices
• C. Actuators
• D. Resistors

Answer: (A)

Continuous-valued signals describe inputs and outputs that can vary across an essentially infinite set of values. In PLC terms, analog devices provide these signals, since they can represent many different voltages or currents (for example, 0 to 10 V or 4 to 20 mA), letting a system respond to a wide range of conditions rather than just on/off states.

Discrete devices, by contrast, switch between distinct states—typically two (like 0 or 1). That’s why they aren’t described as having infinite states. Actuators are devices that perform actions or movements, and while some can be controlled by varying signals, the term doesn’t describe the state richness of the input/output alone. Resistors are passive components used to set or sense current and voltage; they aren’t described as providing a multi-state input/output capability in the control sense.

So the term that best describes inputs and outputs with infinite possible states is analog devices.