This circuit was found in a publication by Edelman from 1924. The power comes from the battery and the listening is through a high-impedance headphone.
This sensitive medium wave (MW) radio pick up the local station without the need of an external...
This audio circuit was published in a Rado Electronics issue from October 1963. The transistors are from...
Using a V/F converter this circuit was found in the June 1991 issue of Radio Electronics magazine. The...