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.
This circuit appeared in the 1991 Electronics Experimenter Handbook. The circuit is for remote...
This circuit was found in Radio Electronics magazine from January 1959. The power transistor must...
This circuit uses an MW radio tuned to around 540 kHz to detect atmospheric signals, for example, from...