The HM-RHSE-S2 uses the same thermistor and microprocessor technology to provide an alarm when the rate of rise in temperature exceeds 10°C/minute (typical) or if the temperature exceeds a thresholds of 58°C (Response class A1R). With the implementation of the Advanced Protocol, any model can be software configured to be either a fixed 58°C, a fixed 78°C unit or a 58°C with rate of rise device. For backwards compatibility and approval continuity, three separate versions continue to be available as separate part numbers.