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 1968 circuit is intended to switch the polarization of a satellite TV antenna of the time. The...
Using an integrated circuit from the time, we found this configuration in a 90s Radio Electronics....
Found in a 90s Popular Electronics, this circuit is based on a uA739, an unusual component today....