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 traditional configuration found in a Radio Shack document can use 2N2646. More keys can be...
This is the circuit of a turntable from the 1970s. We found it in a repair article in the December...
Using the CA3018 released at the time, this circuit was found in the August 1970 Radio Electronics...