We found this circuit in a 1976 documentation. The FET can be BF245 or MPF102 and the power supply need not be symmetrical. The FET in the feedback acts as an automatic gain control.
This tone generator for CW was found in a publication by Gernsback from 1960. The circuit makes use...
This circuit was obtained in an old US 1974 documentation when Nixie tube displays were common. The...
This circuit was found in an 80s National Semiconductor documentation. The configuration holds...