This circuit was obtained from a Hands-On Electronics, an American magazine from January 1987. The purpose of this circuit is to light an incandescent lamp when the power goes out of power. The neon lamp keeps the circuit inhibited and when it goes out, the phototransistor detects activating the circuit. The NPN transistor can be the BC548 and the PNP the BC558. The 6 to 12 V supply must be according to the lamp used.
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