This circuit was found in a 80s American documentation. The zener diodes determine the points of action of each stage and the transistors can be general purpose types.
This receiver for the mid-wave band was found in a documentation from the 60's. The transistors are made...
This circuit was obtained from an English magazine from 1977. The magazine no longer exists, but...
When a voice signal enters this circuit, the volume of the music being played automatically...