In summary, a PhotoMOS consists of an LED and a photo array which are molded in a translucent resin. This allows light to pass through and provides a dielectric barrier between the input and output. To operate the relay, a current is applied to the LED on the input. The photoelectric element absorbs the light that is generated and converts it to an electric current which then passes through a control circuit to charge the gates of the two MOSFETs on the output side. Upon reaching the preset threshold, the MOSFETs begin to conduct and permit the load to pass through. This process is terminated when the LED is turned off, the gate rapidly discharges, forcing the MOSFETs to stop conducting and turn off the load. Solid-state relays avoid the common failure modes of mechanical relays, because they contain no moving parts. Photo-optical MOSFET relays such as PhotoMOS have highly linear input and output characteristics that out-perform alternatives and can control small analog signals without distortion, unlike Triacs and bipolar transistors whose offset voltages distort and clip signals.