The circuit is from 1994 National Semiconductor documentation. The component is not easy to obtain, but there are equivalents that can be searched.
This circuit combines field effect and bipolar transistors to obtain a 20 gain with a pass band...
We found this simple toy organ circuit in the February 1968 issue of Radio Electronics magazine. The...
The sensor for this alarm is a thin wire that, when interrupted, triggers a buzzer and turns on a...