The input and output frequencies of this circuit depend on the coils and capacitors of the tuned circuits. The circuit is from Electronics Now magazine, February 1997.
This circuit was found in Electronics Now. With it the dialing signals of a telephone are...
Found in American documentation, this simple circuit activates a buzzer with embedded oscillator. A...
I found this circuit in an old English magazine from 1979, but it can be easily assembled with...