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 for signals around 4.5 MHz for old analog TV was found in the September 1992 Radio...
The circuit shown is a commercial electronic voltmeter sold in Japan in the 1960s. The circuit is fully...
This 80's circuit can be implemented with modern equivalent FETs with lower on resistance. The...