There's two types of fixed temperature detectors: linear detectors, which keep track of the temperature all through an area, and spot detectors, which observe the temperature in a single precise site. According to the Countrywide Hearth Alarm and Signaling Code, some of the higher than are “hearth safety capabilities” meant https://www.firesense.co.uk/type/addressable-fire-system/addressable-beam-detectors/