Monitor/control abstract model

Sensor constantly monitors a physical effect.
Sensor sends reading to microprocessor.
Microprocessor has been programmed with thresholds for the physical effect.
If reading goes beyond threshold,
 - then microprocessor sends signal to actuator (that controls means to modify physical effect), to change state.
If reading from sensor is back within specified range,
 - then microprocessor sends signal to actuator to reset state.