This circuit was found in a Signetics documentation from the 1980s. The integrated is a PLL and the SCR is a general purpose type The pitch frequency is given by R1 and C1 as formula next to the diagram.
Suggested to power the previous circuit, this power supply was found in the December 1990 issue of...
This is a very useful autotransformer circuit on the bench. We found it in the September 1970...
This circuit was obtained in a 1960 documentation of General Electric. It is applied in the...