This simple bridge circuit can be used for impedance or resistance measurement using a high impedance earphone as an indicator. The circuit is from an American 80's documentation.
The 556 integrated circuit is actually a double 555. This circuit can be assembled from an...
The transducer used in this configuration that appears elsewhere on this site is a piezoelectric...
This modern XTAL radio replaces the galena crystal for a germanium diode as the 1N34 or...