Process and temperature controllers are small, integrated devices used to maintain a process variable, usually temperature, at some desired set point. Typically making use of a sensor such as a thermocouple or RTD that is located external to the controller, the simplest of these devices is similar in function to a common household thermostat, providing an on/off signal that can be used to control a device such as a heater or furnace to maintain a temperature at some desired set point. More advanced devices add higher level communications capability and more sophisticated control algorithms to improve connectivity and temperature control performance.