What do locators detect?

• A. Light reflections
• B. Acoustic vibrations
• C. Thermal signals
• D. Electromagnetic signals radiating from metallic wires and pipes

Answer: (D)

Locators are designed to sense the electromagnetic energy that comes from buried metallic lines. When current flows in wires or pipes, it creates an electromagnetic field that reaches the surface, and the locator’s receiver picks up that signal to trace the line and estimate depth. This is what makes the option describing electromagnetic signals radiating from metallic wires and pipes the correct choice. The other options describe sensing methods not used by standard locators: light reflections involve optical methods, thermal signals relate to heat imaging, and acoustic vibrations rely on sound or vibration detection rather than EM fields.