| 摘要 |
A lighting system comprises a set of parallel connected flasher lamps (24, 26, 30, 34) driven by an astable multivibrator (14). A bridge circuit detects the current flowing in the lamps and comprises a first resistor (R7) connected in series with the lamps, second and third resistors (R9, R11) connected in series across the lamps, and a transistor (T3) having its base-emitter path connected between the junction of the first resistor and the lamps and the junction of the second and third resistors. The transistor (T3) control the frequency of the multivibrator (14) so as to provide an indication of lamp failure. In order to compensate for the variations of the resistance of the lamps with supply voltage, a zener diode (ZD1) and a fourth resistor (R13) are connected in series across the second and third resistors, and a fifth resistor (R10) is connected between the junction of the second and third resistors and the junction of the fourth resistor and the zener diode.
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