This circuit activates a buzzer when the voltage applied to the input falls below a preset value in R1. The circuit is from an 80's American documentation.
This circuit is from an old Italian publication, being used in record players with crystal...
This is the traditional circuit from the 1980 racing video game with the AY3-6603-1 that we also...
This interesting game was found in a 1987 publication, but it is very simple and can be easily...