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 SCR relaxation oscillator was found in old documentation. The SCR can be TIC106 and the...
The oscillator shown in the figure generates a 1 kHz tone that is reproduced on the speaker with...
Suggested by an Electronics Now magazine from April 1994, these circuits can be used as output...