This circuit was obtained from American documentation from the 1990s. The transformer can be a car ignition coil that works like an autotransformer. Q2 must be equipped with a heat sink.
To use the instrument for AC measurement, the tips are A and B. For CC use tips A or B for...
The interesting circuit shown in the figure, can have its gain digitally controlled and present two...
This simple MW radio was found in a 1975 publication, but it can be mounted with BC548...