The maximum frequency of this circuit is 500 kHz. We found it in a documentation for radio amateurs from the 1980s. The integrated circuit used is uncommon today.
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...