In PLC terminology, a stand-alone PLC is characterized by which of the following?

• A. It contains all major sections in a single unit
• B. It relies on separate racks
• C. It requires a separate CPU
• D. It uses external power supply

Answer: (A)

A stand-alone PLC is a single self-contained unit that houses the CPU, I/O interfaces, memory, and power inside one enclosure. This integration means there’s no need for separate racks or backplanes, and the CPU isn’t a separate module—it’s built into the unit. The power supply is typically built in as well, so external power isn’t required. This contrasts with modular or rack-based PLCs, where CPU, I/O, and power are distributed across multiple modules in a frame. That integrated, all-in-one design is what makes the stand-alone description fit best.