In this circuit the LED lights up when the voltage drops below the value set in the trimpot. The transistors can be the BC548. The circuit is from a 1999 American publication.
I found this circuit in an article in a 2003 publication. The circuit is an example of how to...
This circuit drives a buzzer or electric buzzer but can be used to trigger a relay or other load....
May 2017 - Mouser Electronics is already in stock with the new BCP1395 transistors from Nexperia....