The diagram shows a tone control with the LM381 IC. The circuit is from a Radio Electronics from February 1990. The power supply is simple.
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...