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.
Found in a 1960 Sylvania manual, this circuit can be implemented with a modern equivalent...
This configuration, already presented in other points of this section and website, is of a...
We found this precise crystal oscillator for the 144 MHz band, depending on the crystal used. The...