This circuit for frequencies of 20 to 2 kHz was obtained in English documentation from 1966. The transistor can be any general purpose and powered by batteries.
This circuit was found in a 1994 Electronics Now. The circuit uses an old analog TV flyback and...
This circuit was obtained from a 1965 magazine, but can still be assembled if we use a modern 6 V...
This circuit appeared in Radio Electronics in November 1984. The frequency depends primarily on...