This commercial radio with 3 earphone listening transistors was manufactured in Japan in the 1960s. The medium-wave circuit uses germanium transistors and is powered by a 9 V battery.
The integrated circuit used in this project is not common today, but it can be implemented with more...
Found in an American publication from 1969, this circuit can be adapted to be used as a shield....
This current meter with many scales was found in a 80s American documentation. The operational amplifier...