The circuit was found in the February 1992 Radio Electronics magazine. The scale can be changed by changing R2 and R3.
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....