Solid-state relays can switch the fastest and have essentially infinite life.

Solid-state relays control power circuits with no moving parts, instead using a semiconductor device to perform switching.

Solid-state relays rated to handle as much as 1,200 amperes have become commercially available.

To reach the required threshold, solid-state relays contain stacks of up to thirty photodiodes wired in series.

"Those are solid-state relays."

A solid-state relay (SSR) is an electronic switching device in which a small control signal controls a larger load current or voltage.

A solid-state relay uses a thyristor or other solid-state switching device, activated by the control signal, to switch the controlled load, instead of a solenoid.

Solid-state relays built around MOSFET switches usually employ a photodiode opto-isolator to drive the switch.

The input/output circuits usually do not provide enough current to directly operate such devices as lamps or motors, so solid-state relays are operated by the microcontroller digital outputs, and inputs are isolated by signal conditioning level-shifting and protection circuits.