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 high impedance input amplifier is suitable for the use with piezoelectric sources such as...
The circuit shown is based on National Semiconductor buffers and was found in the 1994 Linear...
This circuit was obtained in a1969 magazine. The magazine no longer exists, but the circuit can be...