Electrolytic detector, consisting of a metal cup with nitric acid and a fine platinum wire with the tip dipping in the acid.
An electrolytic detector, or liquid barretter, is a type of detector (demodulator) used in early radio receivers. It was first used by Canadian radio researcher Reginald Fessenden in 1903, and used until about 1913, after which it was superseded by crystal detectors and vacuum tube detectors such as the Fleming valve and Audion (triode).[1][2] It was considered very sensitive and reliable compared to other detectors available at the time such as the magnetic detector and the coherer.[3] It was one of the first rectifying detectors, able to receive AM (sound) transmissions. On December 24, 1906, US Naval ships with radio receivers equipped with Fessenden's electrolytic detectors received the first AM radio broadcast from Fessenden's Brant Rock, Massachusetts transmitter, consisting of a program of Christmas music.[4][5]
^Belrose, John S. (5–7 September 1995). "Receiver Technology". International Conference on 100 Years of Radio. IEEE. Archived from the original on 28 December 2012. Retrieved 28 July 2010.