Relays are electromechanical or solid-state devices used to control high-power circuits with a low-power signal. They act as switches, enabling the isolation and protection of control circuits from high-voltage or high-current loads. Common types include electromagnetic relays, reed relays, and solid-state relays (SSRs). Key features include fast switching, high durability, and compatibility with various voltages. Typical products in this category include time delay relays, latching relays, automotive relays, and overload protection relays. They are widely used in automation, industrial control systems, and power distribution applications.