Explanation: An electrical relay is an electromechanical switch. It operates by using a small control current to energize an electromagnet. This electromagnet then physically moves a set of contacts, which in turn opens or closes a separate, often higher-power, electrical circuit. This allows a low-power signal or a signal from a remote location to control a different circuit, making it a remotely controlled switching device. Therefore, option D is correct. Option A is incorrect; current limiting devices are components like resistors or fuses. Option B describes a multi-output power supply or voltage divider, not a relay. Option C is too specific; while relays are used in many radio circuits, including sometimes in HF amplifiers for switching functions, their primary characteristic is not limited to this application.