When the environment is hot in the heat sensitive circuit, the voltage on the NTC decreases. T2 switches to cut, T1 switches to transmission. Relay contacts change position. When the environment is cooled, the voltage falling on the NTC increases. T1 transmission is T2 cut. These changes are caused by the variation of the resistance of the NTC element to the heat.
HEAT-SENSITIVE CIRCUIT DIAGRAM WITH TWO TRANSISTORS NTC SENSORS
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