Controller input and output modules have opto-isolation to prevent noise and operational problems. True or False?

• A. True
• B. False
• C. Not sure
• D. Not applicable

Answer: (A)

Opto-isolation between control electronics and field wiring prevents noise and transients from propagating into the controller. In input and output modules, isolators use an LED and a photodetector (or similar optocoupler) so the signal is transmitted without a direct electrical connection. This means ground differences, voltage spikes, and EMI on the field side can’t easily reach the control circuitry, protecting the logic and reducing erroneous operation. It’s a common and deliberate design choice to improve reliability and safety, which is why the statement is true. The other options don’t align with standard practice: not sure or not applicable aren’t meaningful here, and false would ignore the widely used practice of opto-isolation in I/O modules.