Lighting contactors are commonly controlled by which two-wire pilot device?

• A. Time clock
• B. Thermostat
• C. Photoelectric relay
• D. Pushbutton

Answer: (A)

A lighting contactor is energized when a pilot device closes the control circuit feeding the coil. A two-wire pilot device uses only two conductors and doesn’t need a separate power supply for the pilot; it taps the same line voltage that powers the load to signal the coil. A time clock fits this role because it provides an automatic, timed signal to close the pilot circuit and energize the contactor at programmed times, turning lights on and off without manual action. While other options can control lighting in different ways (thermostats for temperature control, photoelectric relays reacting to ambient light, pushbuttons for manual control), the time clock is the classic two-wire pilot device for automatic lighting control in commercial settings.