Discrete controllers which, when a certain control deviation is exceeded, change the suddenly at various stages (DIN 19 225).
Example based on a two-point controller: temperature control via a device whose contact switches the heating off by means of a contactor when a limit value is reached.
Example based on a three-point controller: temperature control for heating and ventilation based on three values associated with the actuator with mechanically controlled valve such as ventilation valve open, both valves closed and heating valve open.