This signal conditioner humidity sensor was found in a 1980s Linear Technology documentation. The circuit uses components from the era that can be designed with modern equivalents.
This circuit allows the activation of a remote telephone bell made with a common piezoelectric capsule. The...
This circuit for analog VHF televisions was found in the 1989 Radio Electronics Experimenter...
The assembly of this circuit with 3 transistors was described in an article in Radio Electronics magazine...