Which of the following is NOT a major hardware component of a PLC?

The communication modem is not considered a major hardware component of a Programmable Logic Controller (PLC). PLCS primarily consist of three fundamental components: the processor, input module, and output module.

The processor is the brain of the PLC, executing control programs and processing the logic that dictates how the PLC responds to input signals. The input module facilitates the connection between the PLC and external devices, allowing it to receive data from sensors and other devices. The output module, in turn, sends signals to actuators or other output devices based on the processed input.

While communication modems can be used with PLCs to enable data exchange over long distances and integrate with other networks or systems, they serve as auxiliary components rather than core ones. Thus, they do not fall into the primary categories of hardware essential to the fundamental operation of a PLC.