Found in a 1924 documentation, this circuit is powered by 3 batteries, two of which are high voltage. The output is a high impedance headphone jack.
Found in a publication for radio amateurs from the 1990s, this circuit makes it possible to...
I found this circuit in a Popular Electronics from November 1999. The magazine is no longer...
This simple transistorized receiver with earphone was found in a Japanese publication from the...