A Control Relay is an electromechanical device used to control a circuit by opening or closing contacts in response to an electrical signal. It acts as a switch that can be activated by a low-power signal, allowing it to control larger loads without direct electrical connection. This makes it essential in various applications, such as automation systems and safety devices. Control relays are commonly used in conjunction with other components like sensors, timers, and programmable logic controllers (PLCs). They help manage electrical systems by providing isolation and protection, ensuring that the main circuit operates safely and efficiently.