#$%^&*AU2008237548B220130207.pdf#####REDUNDANT POWER CONTROL FOR RESPIRATORY SYSTEM HEATERS Abstract A humidification system is provided for a respiratory system is provided with a controller (54) having two processors (150, 152) that monitor the operation of each other and of heating elements (34, 36, 56) in the respiratory system to provide CPU redundancy and heating element control. Each heating element is provided with two control paths (74, 142； 77,146； 79,146), for example a relay (140 or 144) and a triac (88) connected in series with the heating element and a power supply (90). Each heater element has one control path connected to a first one (ISO) of the processors and at least one heating element has at least one control path connected to a second one (152) of the controllers. A hardware watchdog (100) monitors the operation of the first processor, and can be triggered by a signal from the second processor, in response to which it can disable all heating elements.7 3/4 MAIN CPU RELAY 2 5 4 OE HARDWARE I HEATER WATCHDOG CIRCUIT -- TI58 7 3 R INSPIRATORY CIRCUIT Ifi 174 FIG. 3 _I
