| 摘要 |
PURPOSE:To prevent a shift of a detection level by providing a PNP transistor connected to a variable resistance to change a detection level and NPN transistor connected to a fixed resistance to fix a detection level. CONSTITUTION:In case of controlling a temp. detection level with variation by variable resistance of slide volumn, etc., the level of the output O-O of a microcomputor 1 is on a level ''L'' and transistor Tr 22, 26 are OFF and so an electric current is not flow to a fixed resistance 14 but Tr 25 is turned on conversely and an electric current is flowed to a variable resistance 13. So the input level of the plus input terminal of a comparator 2 is decided by the resistance values of the variable resistance 13 and a thermistor 12. When an energy saving operation is started with turning-on of a switch 18 the level of the output O-O of the microcomputor 1 becomes a level ''H'' on receipt of this signal. The Tr 26 is turned ON thereby and an electric current is flowed to the fixed resistance 14. A Tr 25 is also turned off and an electric current is not flowed to the variable resistance 13. Consequently the input voltage level of the plus input terminal of the comparator 2 is decided by the resistance values of a fixed resistance and thermistor. |
