We found this circuit in a documentation from the 90's. The coil has its characteristics given next to the diagram. Power is provided by a 9 V battery and a range of a few tens of meters.
The correct connection of speakers and tweeters in a speaker to obtain better sound quality,...
This circuit with germanium transistors was found in a Mullard manual from 1960. The components depend...
This circuit was found in a Popular Electronics from the 90s. The components admit equivalents and the...