This gas sensor circuit was found in July 1976 Radio Electronics magazine. The TGS sensor was a common type at the time. Note the power supply to the circuit.
This low frequency circuit was found in documentation from the 1980s. The values of R and C...
This source for devices for automotive use was found in a 1985 documentation. The power...
Found on Popular Electronics in the 1980s, this circuit detects a change in air pressure using a...