Found in a 90s Popular Electronics, this circuit uses general-purpose transistors, serving to indicate the polarity of circuits.
n be assembled with BC558 transistors for low power transistors and a BD136 for the output. The...
In the figure we have the way to use a zener instead of a filter capacitor. The zener can have the...
This circuit was obtained in a 1965 American magazine translation. The coil is formed by 40 + 40...