This TTL circuit was found in an American documentation from the 80s. The components are common in the series and the supply must be made with a voltage of 5 V.
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...