In which PLC configuration are the processor, power supply, I/O modules, and communication modules all housed in a single unit?

• A. Stand-alone
• B. Modular
• C. Distributed
• D. Networked

Answer: (A)

All components are in one compact unit, which is what a stand-alone PLC is. In this setup, the processor, power supply, I/O modules, and any communication interfaces are all built into a single enclosure. That makes the controller quick to deploy and simple to wire, with a small footprint and limited but sufficient expandability for smaller applications.

If you were to use a modular configuration, you’d see the processor, power supply, and I/O in separate modules that sit on a backplane or rack, allowing easy expansion by swapping or adding modules. A distributed configuration places I/O physically near the field devices and connects it back to the controller over a network, so the controller and I/O aren’t in the same cabinet. A networked setup involves multiple PLCs or controllers communicating over a network, coordinating across devices rather than all being housed in one unit.