This crystal or galena radio was found in documentation from the 1990s. The earpiece must be a high impedance crystal or magnetic earpiece and D1 can be any germanium diode.
This circuit was found in an English publication from 1967. The circuit is for listening on a...
This circuit allows you to use a digital multimeter as a thermometer. The sensor is mounted in a...
This configuration, which appears in other articles on this website, was found in a European...