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.
Found in a 90s 73 magazine for radio amateurs, this circuit makes use of common operational...
Found in a 90’s Electronic Engineering, this circuit detects the lack of phase in the supply of a...
It can be obtained from Mouser Electronics the new MAX14871 Maxim consisting of a full-wave...