A solid-state relay (SSR) is an electronic switching device that switches on or off when an external voltage (AC or DC) is applied across its control terminals. ... Solid-state relays have fast switching speeds compared with electromechanical relays, and have no physical contacts to wear out. Specifications: Brand: Chygm Model: SSR-A48 40A Origin : Asia Pacific Power supply: AC Color classification : SSR - A48  40A Contact forms: normally open type Package Includes: 1 x Solid State Relay SSR-A48 40A (Chygm)