Found in a 1924 publication, this 2-valve receiver has a speaker output. Power comes from several batteries. Information about the coils is given.
This current-limited circuit was found in a Popular Electronics from the 90's. ...
In this interesting circuit, a common relay is used as a vibrator to obtain high voltage with a...
Nixie-type displays are no longer used except for assemblies of people who like old technology. The...