The figure shows a remote-control receiver working the 27 MHz band, very popular in the 60’s. The circuit us from a February 1961 Radio Electronics magazine.
The transformer for this project found in a 1986 documentation is an output type, found on old...
This circuit was found in a Popular Electronics from the 90's. It can be implemented with...
This basic configuration can be found in a lot of articles on this site. In this case, the relay...