| 摘要 |
PURPOSE:To improve reliability of an apparatus for detecting disconnection of a plurality of lamps by connecting the output terminal in a hall 1C8 for detecting disconnection to an indicator through a drive circuit comprising a base resistance, first and second transistors, etc. CONSTITUTION:When a main switch 1 is closed, a brake switch 2 is opened and power supply in hall 1C8 is not yet made. The output is at ''L'', level, a first transistor 92 is under the off-condition and a second transistor 94 is turned on to light a indicator 10. When an open/close switch 2 is closed, load lamps 4a, 4b come on, while the size of combined magnetic field of a current coil 3 and subcurrent coil 6 is normally two lamp lighting magnetic field subtracted by coil 6 magnetic field, i.e.1-alpha. This magnetic field is added to 1C8 and the foutput is at ''L'' level to turn off the transistor 92. The size of magnetic field in the case of one lamp disconnection is -alpha and in the case of both two lamp disconnection is -(1+alpha), both turning off the indicator 10. |
