Editing Echo sounding (section)

== History ==

German inventor [[Alexander Behm]] was granted German [[patent]] No. 282009 for the invention of echo sounding ''(device for measuring depths of the sea and distances and headings of ships or obstacles by means of reflected sound waves)'' on 22 July 1913.<ref>{{cite book | url=https://books.google.com/books?id=3Al4uqB66KUC&q=alexander+behm+echo+sounding&pg=SA3-PA61 | title=Radio Propagation Measurement and Channel Modelling | publisher=[[John Wiley & Sons]] | author=Salous, Sana | year=2013 | pages=424| isbn=9781118502327 }}</ref><ref>{{cite book | url=https://books.google.com/books?id=RFMQd__GtSMC&q=alexander+behm+inventor+echo+sounding | title=Sciences of Geodesy - I: Advances and Future Directions | publisher=[[Springer Publishing]] | author=Xu, Guochang | year=2010 | pages=281| isbn=9783642117411 }}</ref><ref>{{cite web | url=http://www.alexander-behm-echolot.de/ | title=Alexander Behm - Der Erfinder des Echolots | access-date=9 April 2014 | author=Werner Schneider}}</ref>
Meanwhile, in France, physicist [[Paul Langevin]] (connected with [[Marie Curie]] and better known for his research work in [[nuclear physics]]) was recruited by [[French Navy]] laboratories at the beginning of World War 1 and conducted (then secret) research on active sonars for anti-submarine warfare (using a [[Piezoelectricity|piezoelectric transmitter]]). His work was developed and implemented by other scientists and technnicians such as Chilowski, Florisson and Pierre Marti.{{Fix|text=These don't have their own articles. Are they notable?}} Though a fully operational ''échosondeur'' (sonar) was not ready for use in wartime, there were successful trials both off [[Toulon]] and in the [[English Channel]] as early as 1920, and French patents taken for civilian uses. Oceanographic ships and French high-sea fishing assistance vessels were equipped with Langevin-Florisson and Langevin Marti recording sonars as early as the mid/late 1920s.<ref>{{cite web | url=https://www.academia.edu/1182631 | title=Paul Langevin et la detection sous-marine, 1914-1929. Un physicien acteur de l'innovation industrielle et militaire (Epistemologiques, 2001) | last1=Lelong | first1=Benoit }}</ref>

One of the first commercial echo sounding units was the Fessenden Fathometer, which used the [[Fessenden oscillator]] to generate sound waves. This was first installed by the Submarine Signal Company in 1924 on the M&M{{clarify|date=August 2024}} liner SS Berkshire.<ref>{{cite web|title=Fessenden Fathometer amplifier - Submarine Signal Company|url=https://www.subchaser.org/fathometer|website=The Subchaser Archives|date=20 March 2007|access-date=12 April 2018}}</ref>