This is a low-gain amplifier to operate as a booster. We found it in an American documentation from 1947. The circuit uses a coupling transformer at the input.
This circuit was found in a 90s Popular Electronics. The sensors can be common speakers that reach...
This variable oscillator with crystal was found in a Popular Electronics of the 90s. The circuit uses...
This sensor circuit was found in an American 1980s documentation. Modern operational amplifiers can...