Found in a 1990s American documentation, this circuit provides an output voltage approximately 4 times that of the input voltage. Diodes are general-purpose types.
This 1950's circuit used one of the first commercial transistors and had two stages for audio...
Using integrated circuits from the time, we found this audio compressor in an English publication from...
This is an experimental crystal radio that uses no power source. The antenna must be very long (at...