| 摘要 |
PURPOSE: To detect the position of a lamp, from which the wick has run out, among a large number of lamps by providing each lamp with a variable impedance and varying the impedance of each lamp at a different frequency. CONSTITUTION: A current is fed from an AC power supply 1 to a constant current power supply 2 for feeding power to a lamp lighting circuit 5. Each of a plurality of current transformers CT1 , CT2 ,..., CTn connected in series is connected, on the secondary thereof, with a series circuit of lamp L1 , L2 ,..., L∼and a terminal part RA1 , RA2 ,..., RAn . Each terminal part RA1 , RA2 ,..., RAn comprises a variable impedance and an impedance control section. The impedance control section varies the variable impedance of each lamp L1 , L2 ,..., Ln at a different frequency thus modulating the output waveform of the power supply 2. A waveform filter 6 outputs the modulated frequency components from the voltage of power supply 2. The position of a lamp where the wick has run out is determined at section 7 based on the magnitude of modulated frequency component outputted from the filter 6.
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