Circuit of an early radio receiver with electrolytic detector, from the very start of the 20th century. A battery and potentiometer apply a small bias voltage to the electrolytic detector. The electrolytic polarization of the anode is very fast. The anode is a very fine platinum wire  1/100 of millimetre in diameter, while the cathode is a lead or platinum plate or large wire.   The alternating signal from the tuned circuit partially depolarizes the anode in response to the amplitude modulation, which draws a DC current from the battery which varies with the modulation, to repolarise the anode. This current passes through the earphone, which converts the audio current to sound.  The electrolytic detector functions with a bias voltage of between 1.5 and 2.5 volts.  To adjust it, the bias voltage is first adjustad to maximum, 2.5 volts. As soon as water bubbles indicate that electrolysis is occurring, and a noise is heard in the earphone, the bias voltage is slowly turned down until the noise completely disappears.  Then the antenna is connected.  The detector must be readjusted in the event of a change of temperature, barometric pressure, vibration, or shock.   The electrolytic detector has a sensitivity of 7 nanowatts. It is unstable when subjected to movement or vibration, so it is only usable in fixed stations, not in portable or mobile radios, ships, aircraft, or airships.  It was only used in early receivers for a short time due to its complexity of maintenance.
File:Poste détecteur électrolytique.JPG by F1jmm
Д.Ильин: vectorization, translation