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 . ... Packaged solid-state relays use power semiconductor devices such as thyristors and transistors, to switch currents up to around a hundred amperes. Video Specification: Brand Name: Tense Theory : Solid State Relay Model Number: SSR-ZX40DA 40A 24-480VAC Protect Feature : Sealed Usage : General Purpose Size : Subminiature Package includes: 1 x Tense Solid State Relay SSR-ZX40DA 40A 24-480VAC