This unusual circuit from a Popular Electronics of the 90s uses LED indicators, operating as a bridge. The components used are common. It is based on the tuning of the signal by a PLL.
This circuit was found in old documentation. It can be made based on modern components. The time...
This small two-transistor AM radio was sold in the 1960s in Japan. The circuit was powered by two...
I found this circuit in an old English magazine from 1979, but it can be easily assembled with...