An alarm circuit for detection of an overheated condition comprises a bridge rectifier or a battery to provide a d.c. input, and a detector bridge including a thermistor and Zener diode in adjacent arms. The diode is set to operate along that portion of the thermistor response curve which is slowly changing....http://www.google.fr/patents/US4278970?utm_source=gb-gplus-shareBrevet US4278970 - Alarm circuit for detecting overheated condition
