Submarine chaser SC 19 is shown in these photos with experimental listening equipment. The chaser was engged in test runs of different configurtions of "tubes," which led to the development of the several tube devices used on chasers in the war -- the C Tube Hydrophone being the most widely distributed in the U.S. chaser fleet. SC 250 is also shown in one photo, with MF Tube mounted.
Photos courtesy of the Harvey Hayes Family Archives. Thanks to Roy Manstan for the scans, and for arranging permission to post them in The Subchaser Archives.