Supervisory circuits are electronic circuits used to monitor and control the operation of other circuits or systems. They are commonly found in appliances, industrial equipment and other electronic systems where reliable operation is required. Supervisory circuits monitor and control the behavior of other circuits and systems, providing feedback and making adjustments as necessary to keep them within acceptable parameters. They are generally composed of several parts, including sensors, comparators, alarms, timers, and relays. The sensors monitor the voltage, current, and temperature of the circuits and systems, while the comparators compare these values to normal operating parameters. Alarms are triggered when parameters are out of range, while the relays are used to activate corrective actions, such as turning off equipment or engaging a fail-safe mode. Timers are typically used to monitor the length of time a certain condition has been present, allowing the supervisor circuit to shut down the system before it is damaged by an enduring failure.