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.
August 2016 - It can be obtained from Mouser Electronics the new DC-DC PFM Step-Down XC9272 from...
We found this circuit in a European publication from the 1970s. The transistors are made of...
This circuit operates from 20 Hz to over 20 kHz and is easily tunable. We found it in a 70s...