What type of circuit controls another circuit through a relay?

The correct answer is the remote-control circuit. A remote-control circuit is specifically designed to activate or control another circuit through the use of a relay. This setup enables the control of larger electrical loads or systems from a distance, providing the operator the ability to manage power without directly interacting with the higher voltage or current circuit.

In a remote-control circuit, the small control signal can activate a relay, which then closes or opens the circuit of a different, often more complex, load. This type of circuit is essential in various applications, such as automation systems, where a small controller can operate equipment located far from the power source.

The other types of circuits do not fit this specific definition. A control circuit typically refers to a basic circuit that manages the operation of devices but is not necessarily designed for remote operation through a relay. A feeder circuit is intended for transporting electrical energy from a service point to distribution points, and a branch circuit delivers power to the final load but does not operate or control another circuit remotely.