A monitoring device, the STCC08, can be seen on this slide. When the Triac is turned on with a signal from the microcontroller, the STCC008 makes sure that the Triac turns on properly, that it is conducting in both directions, not only in one direction, and also makes sure that it turns off.  When the microcontroller instructs the Triac to turn off, the STCC08 monitors to verify that the Triac is indeed turned off. It is a device that is used to detect failures in the main AC switch in applications that are critical, for example controlling valves in dishwashers or washing machines that fill or add water to the appliance. If the Triac did not turn off and the valve stayed open, the dishwasher or the washing machine would flood.