Graphs of the <a href="https://en.wikipedia.org/wiki/Detector_(radio)" class="extiw" title="wikipedia:Detector (radio)">detection</a> (demodulation) process for <a href="https://en.wikipedia.org/wiki/Amplitude_modulation" class="extiw" title="wikipedia:Amplitude modulation">amplitude modulated</a> (AM) radio signals, adapted from a 1922 radio book.  <i>(A)</i> The amplitude modulated signal applied to the detector. <i>(B)</i> The signal at the output of the detector.  The detector allows current in only one direction, stripping off the excursions of the signal on one side.  <i>(C)</i> After filtering.  The filter smoothes the output, removing the radio frequency carrier pulses, leaving the audio frequency signal (modulation).  Alterations to image:  added vertical axis to top drawing, and colored labels.
Harry J. Marx or Adrian Van Muffling
1922
Downloaded <a href="//commons.wikimedia.org/w/index.php?title=2010-01-20&amp;action=edit&amp;redlink=1" class="new" title="2010-01-20 (page does not exist)">2010-01-20</a> from <a rel="nofollow" class="external text" href="https://books.google.com/books?id=BgY9AAAAYAAJ&amp;pg=PA43">Harry J. Marx, Adrian Van Muffling (1922) <i>Radio Reception: A simple and complete explanation of the principles of radio telephony</i>, G.P. Putnam's sons, New York</a>, p.43, fig.27 on Google Books