Apollo Discovery Heat Detector is a common profile with ionisation and optical smoke detectors but have a low air flow resistance case made of self-extinguishing white polycarbonate. For the European standard version of the detector, the five modes correspond to five “classes” as defined in EN 54-5. The classes in this standard correspond with different response behaviour, each of which is designed to be suitable for a range of application temperatures. All modes incorporate “fixed temperature” response, which is defined in the standard by the “static response temperature”. Discovery is a range of high-specification, analogue addressable fire detectors and alarm devices. Discovery detectors offer effective false alarm management by a combination of EN 54 approved operating modes and sophisticated algorithms. The Discovery Heat Detector uses a single thermistor to sense the air temperature at the detector position. The thermistor is connected in a resistor network, which produces a voltage output dependent on temperature. The design of the resistor network, together with the processing algorithm in the microcontroller, gives an approximately linear characteristic from 10°C to 80°C. This linearized signal is further processed, depending on the response mode selected and converted to an analogue output. Discovery detectors are designed to be operated with purpose-designed control and indicating equipment that makes full use of their features. Discovery can, however, be connected to any fire control panel which can operate existing ranges of Apollo analogue addressable detectors with the previously noted rule, that the control and indicating equipment must not have a drift algorithm operating on Discovery devices.