What is a relay?

A relay is an electromechanical or solid-state device that acts as a switch. However, instead of being operated manually by a person, it is operated by an electrical signal. When a small voltage is applied to the relay's coil, it creates a magnetic field that physically pulls a set of contacts together or pushes them apart, opening or closing a separate circuit. This mechanism allows a low-power control circuit (like a small switch on a radio front panel) to safely control a high-power circuit (like an amplifier or an antenna routing system) without any direct electrical connection between the two. Distractors like "current-controlled amplifier" or "pass transistor" describe active semiconductor components that amplify or regulate signals, rather than acting purely as an isolated, electrically-controlled mechanical switch.