Discrete I/O are characterized by which statement?

• A. Continuous range
• B. Two states: true on and false off
• C. Analog signals
• D. Random noise

Answer: (B)

Discrete I/O are digital interfaces that read or drive binary states. They operate as on or off, true or false, i.e., 1 or 0. This two-state nature makes them ideal for simple, decisive control like a pushbutton or a switch turning a device on or off, with clear high or low signals. They do not carry intermediate levels.

Analog signals, by contrast, vary across a continuous range (voltage or current values) and are used for measuring or controlling quantities with many possible values. Random noise can be present in any electrical signal, but it doesn’t define discrete I/O—the defining trait is the binary on/off behavior.