It is an improved version of the previous circuit with a voltage follower that reduces the load impedance. The circuit was found in American documentation from the 1980s.
This telegraph monitor was found in an American documentation for radio amateurs from the 1970s. The...
We found this circuit in a European publication from the 1970s. The transistor is made of...
This adjustable source from 2 to 15 V uses transistors from the 60's, as indicated in the...