This circuit was found in a 1980s documentation. Similar configurations appear in the section, but from different sources. The circuit makes use of components of the time.
We found this circuit in a Hands-On Electroncs from the 90s. The circuit uses an LED indicator. Diodes...
This circuit was obtained in a 1973 national publication, translated from an English publication of the...
We found this circuit in a 1983 English magazine, but it can be easily assembled with the BC548...