What is the meaning of the yellow "CAUTION" RF signs?

• A. You are entering an area where you will be exposed to RF levels up to MPE limits—proceed only if trained.
• B. You are entering an area where RF levels exceed MPE limits—protective measures must be taken.
• C. You should evacuate immediately.
• D. You must shut down all equipment before entering.

Answer: (A)

Yellow CAUTION RF signs indicate you’re entering an area where radiofrequency exposure is present but remains within the regulatory limit—the Maximum Permissible Exposure. This means the hazard is real, but controlled, and entry is allowed for people who have proper RF safety training and will follow the established procedures. That’s why the best interpretation is that you may proceed only if trained. If exposure were exceeding the MPE, you’d see signs that call for protective measures or evacuation, not just caution.