The THERMOFLEX® CF/CR Series standard heat detectors are available in single or multiple circuits with open or closed contact configurations. THERMOFLEX® CF/CR Series detectors are available in 135°F, 165°F, 200°F, and 285°F versions. THERMOFLEX® CR Series The CR Series detectors are combination Rate-of-Rise and Fixed Temperature. The Rate-of-Rise function allows the detector to operate when the temperature at the detector increases at a rate of 15°F per minute. The Fixed Temperature portion will cause the detector to operate when it reaches the applicable temperature. The Rate-of-Rise portion of the detector is restorable; however the Fixed Temperature portion is non-restorable.