In summary, Omron’s mechanical relays set the ultimate standard for reliability, ease of testing, and compatibility with momentary voltage drops. They are available in multiple packaging types including slim, ice cube, miniature, and plug-in/socketed configurations. Customers should be able to find a mechanical relay to fit their exact switching requirements. A solid-state relay (SSR) is a relay that does not have a moving contact. In terms of operation, SSRs are not very different from mechanical relays that have moving contacts. SSRs, however, employ semiconductor switching elements, such as thyristors, triacs, diodes, and transistors.