As the name indicates, a solid state relay is an electrical switch comprising solid state or electronic components. Owing to their nature, solid state relays contain no moving parts. Because no mechanical contacts are opened or closed within the relay, there is no arcing or pitting of contact surfaces, thus no wear-out mechanism. As a result, solid state relays can operate for many millions of turn on/turn off cycles with no deterioration in performance. In addition, with no mechanical movement inside, acoustical noise is eliminated. A big advantage in power cabinets that can contain dozens of relays.