This circuit uses a heated filament as a sensor. With the air current it changes resistance, and the circuit detects it. The circuit is from a 1969 EEE.
This flasher was found in an old Hands On, but uses common components. The optocoupler can be...
This circuit with output powers of 2 to 3 W depending on the power supply was found in the...
The L3 coil is what basically determines the resonant frequency, around 1 MHz, in this oscillator found...