This circuit for light modulated in frequency (FM) operating at 50 kHz was found in a 90’s Electronics Now. The circuit has an active filter. Modern equivalent transistors can be used.
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....