The integrated circuit used in this application is uncommon today. The circuit converts capacitances into voltages from 1 to 10 V for a capacitance range from 10 uF to 100 uF.
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...