The logical rack is an addressable unit consisting of how many input and output points?

• A. 128 input points and 128 output points
• B. 256 input points and 256 output points
• C. 64 input points and 64 output points
• D. 512 input points and 512 output points

Answer: (A)

The concept being tested is how PLC I/O is organized and addressed. A logical rack is the addressable chunk of I/O on the PLC backplane, split into two independent groups: inputs and outputs. In many PLC families, each rack can hold up to 128 discrete input points and 128 discrete output points. That means a rack can manage 256 total I/O points, with the inputs and outputs kept separate to keep addressing straightforward. Other capacities don’t align with this standard rack structure, so the 128 and 128 split best matches typical backplane addressing.