This circuit was found in a 73 magazine for radio amateurs of the 90s. The circuit uses two types of indicators, the diodes are for general use. The power supply is 5 V.
We found this circuit in an American documentation from 1964, but it can be easily assembled...
This useful circuit is used to test the insulation of cables, appliances, leaks in high voltage...
Carefully removing (and a lot of work) the cover of a metallic 2N3055 to expose its joints it...