In recent months I've been posting notes on the K-Tube hydrophone that was widely in use on submarine chasers in WWI. It's an ingenious device, but just one of many versions of electronic hydrophone devices produced by Submarine Signal Company. The science of submarine detection was in its infancy, and many different types of these devices were built and tested.
Before I move on to other topics, I thought it might be interesting to look at a couple of similar designs. Photos and notes below are from a folio of Submarine Signal Company devices in the collection of The Raytheon Company.
R-Tube
The R Tube was developed to replace the S.C. tubes on submarines with the idea of getting a greater range and also lessening the liability of damage to the listener's ears when depth bomb explosions occurred. The enclosed housing was of streamline rubber moulded over a hollow casting and an ordinary K-Unit mounted between the two halves. The device worked reasonably well but because of the great success of the Y-Tube was discontinued.
Y-Tube
Y-Tube, produced starting in April, 1918. This listening device is for use from a stationary or moving submarine. It consists of three K-Tube units enclosed in rubber streamlined forms supported in the fork of a triangle and operated in the same manner as a K-Tube. It is much freer from water noise than the "through the hull" C-Tube or M.B-Tube for submarines and has materially longer range.
—Todd Woofenden, editor