The difference between this circuit and the previous one is that it uses PNP transistors. The circuit is from Radio Electronics magazine from July 1968. The frequency depends on R1 and C1.
This Popular Electronics circuit can be found in various versions on this site and in this...
Found in an article in the August 1971 Radio Electronics magazine, this circuit supports sensitive...
This circuit for low frequency signals from the Loran guidance system was discovered in the July...