The First Black Box?

This posting on Modern Mechanix, from the July 1937 issue of Popular Science, suprised me a little.  While I am not surprised that someone had the idea to record air to ground radio transmissions to aid accident investigations in 1937, I do find it interesting that they would use wax cylinders.  That technology seems out of date, even at that time. 

RADIO communications between plane pilots and airport dispatchers are now permanently recorded on wax cylinders by an electrical machine recently installed by the U. S. Bureau of Air Commerce at a California landing field. Reports made by pilots and orders given by dispatchers, kept on file in record form, are thus available to examiners investigating the causes of any accident to a plane.