This 1924 receiver uses a battery for the tube filaments and a high voltage battery for the amplifier and detector circuit. The speaker is kind of high impedance era.
This circuit was found in a 73 magazine for radio amateurs of the 90s. The circuit uses two types...
Using a 4046 PLL, which is not very common nowadays, this circuit was found in the October 1994...
This interesting circuit is nothing more than a joke. Of course it can be used for other purposes....