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 circuit was found in an English publication from 1989. The integrated circuits are of the...
This commercial radio with 3 earphone listening transistors was manufactured in Japan in the...
This circuit for RF measurements at 200 MHz was found in no documentation two years 80. At a...