A discrete input module handles digital on/off signals.

• A. True
• B. False
• C. It handles analog signals
• D. It handles power

Answer: (A)

Discrete input modules are built to read binary states from field devices. Each input channel reports either on or off, high or low, which corresponds to a digital, single-bit value. That makes them ideal for sensors like pushbuttons and limit switches that switch between two states. Because of this binary nature, discrete inputs handle digital on/off signals rather than a range of values.

Analog input modules, in contrast, measure continuous signals such as 4-20 mA or 0-10 V and convert them into multi-bit values for the PLC. The idea of “handling power” isn’t about the signal being read; while the module needs power to operate, its primary job isn’t to supply or manage power to sensors. So the statement that a discrete input module handles digital on/off signals is correct.