This circuit was found in an American documentation from 1969. Indications of the used transistors are not given, but general-purpose types can be tested.
This filter, from an audio publication from 1977, passes the frequency range corresponding to the...
In the figure we have three voltage doubler configurations that can be used in high and low...
This circuit was found in Motorola documentation from 1966. The lamps are according to power and...