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.
The Texas Instruments TPS7A92 integrated circuit consists of a low-voltage (LDO) linear voltage...
Found in a 1969 EDN, this high current circuit, not indicated in the documentation, uses...
This circuit was obtained in a 1991 Electronics Handbook. The publication no longer exists, but...