Which of the following is an application of a control relay?

A control relay is a versatile device that can be applied in various electrical systems to perform control functions by opening or closing contacts based on an input signal. This ability to manage different electrical devices and circuits makes it suitable for multiple applications.

Lighting control is a common use of control relays, as they can effectively manage the on/off switching of lights based on time schedules, sensors, or other control inputs. This allows for automation and energy savings in lighting systems.

In motor control applications, control relays can be used to start or stop motors, manage overload protections, and control the operation of motor starters. They play a crucial role in ensuring that motors function correctly and safely in industrial and commercial settings.

Control relays are also integral to alarm systems. They can be used to activate alarms or notifications when certain thresholds are met, such as opening doors or triggering sensors. This enhances security systems, enabling prompt responses to various events.

Given the broad functionality of control relays across these diverse applications—lighting, motor control, and alarm systems—the answer that encompasses all these uses is appropriate. The wide-ranging utility underscores the significance of control relays in modern electrical engineering and automation.