This simple analog instrument circuit was found in the October 1977 issue of Radio Electronics magazine. The diodes are germanium for greater sensitivity.
We found this circuit in a 1978 publication. It can be implemented with modern transistors like...
This amplification stage circuit with a germanium transistor was found in a 1980s documentation. The...
We found this circuit on Radio Electronics from July 1990. It triggers a relay with a touch of the...