We found this circuit in the July 1988 Radio Electronics magazine. The frequencies are given by capacitor C1 and the voltage input is made at pin 1.
This didactic circuit was found in a 2001 documentation. It presents the result of programming in binary...
This VFO circuit generates signals from 2 Hz to 50 Hz. We found it in Popular Electronics from...
This circuit can be used as a buzzer from 3 different locations, allowing you to identify where it went...