Priniciples of Electromechanical Relay Operation
3.29 Solid State Relays
A basic definition of a totally solid state relay is a device that operates a
load circuit without the use of physical contacts. This relay contains a
transistor or triac which turns on a load circuit. Disadvantages are cost and
higher currents may require external heat sink components. Advantages are
quieter operation, longer life and faster repetitive operations, especially
where counting or numerical operations are concerned.