In general, solid state relays are quite similar to the mechanical relays that have movable contacts. The main difference between both is the fact that there are no actual moving components in an SSR, just like the name suggests. Rather than relying on a physical contact moving to complete the circuit, solid state relays (SSR) employ optical semiconductor switching elements, such as diodes, thyristors, triacs and transistors. In this article, ATO automation will explore these two typical relays and find out more about their differences.