This circuit uses two diodes in a doubling configuration to receive medium-wave range signals. The phone is crystal. We found it in a 1968 American documentation.
The circuit shown is from an old European publication. In it we have the way to activate a relay...
We found this circuit in a European publication from the 1990s. Transistors are still common types...
This circuit was found in an American documentation and can be added to common amplifiers of any...