This configuration is from the 70s, having been found in an American documentation. The transistors can be BC549 for Q1 and BC548 for Q2.
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...