We found this circuit in a Poptronics from 1998. The circuit can be extended to more competitors with another 4011. The power can be made with voltages from 6 to 12 V.
We found this circuit in an Electronic Design from the 80's. The generated tone can be changed as well...
In the figure we have an oscillator circuit by Wien Bridge (Wien Bridge Oscillator). The frequency of...
We found this circuit in Intersil documentation from the 1980s. The circuit applies to other...