The circuit in the figure causes two lamps to flash alternately at a frequency that can be adjusted in P1. One of the NAND ports is used as an oscillator, whose frequency basically depends on the value of C1, while the other ports are configured as digital amplifiers and turned on in parallel to be able to excite two complementary transistors. For small lamps up to 50 mA, low power transistors such as BC548 / 558 can be used. For higher current lamps, the TIP120 and TIP115, mounted on heat radiators, must be used. The supply voltage of the circuit depends on the lamp used. One of the possible applications for this circuit is in emergency signaling, in triangles for automotive use or even in signaling vehicle exits. A source according to the current and voltage of the lamps must be used.
