Schloemilch cell

From 1903, the company Telefunken used an electrolytic cell as a detector, consisting of 2 platinum wires immersed in a vessel with sulfuric acid. In systems with a bias voltage, the cell changed its resistance by electromagnetic waves. As its sensitivity was very high, the detector, named the "Schlömilch cell" after its inventor, replaced the coherer in a short space of time. This detector meant you could use headphones to receive sound.