Direct-acting temperature regulators have a sensing bulb that detects fluctuations in system pressure and responds by closing the valve to regulate temperatures. These regulators are self-operating and do not require any external power source. They have interchangeable components that make them compatible with different liquids and gases, and are used for heating, cooling, and refrigeration systems.

Reverse-acting temperature regulators have a sensing bulb that detects fluctuations in system pressure and responds by opening the valve to regulate temperatures. These regulators are self-operating and do not require electricity, batteries, or other external power sources. They are used for heating, cooling, and refrigeration systems.