This circuit was found in a Popular Electronics from the 90s. The transistors are general purpose, and the gain depends on the ratio between R2 and R1.
The circuit shown here uses a 4047 to produce three signals whose frequencies are determined by C...
We found this circuit in an old English publication. The resistor not indicated can be 2k2 and the...
This circuit was found in documentation from the 1980s. The integrated circuit used is uncommon today...