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Captain (Retired) Oscar W. Koester, Bureau of Steam Engineering, to Rear Admiral William McLean, Commandant, Fifth Naval District



                        WASHINGTON, D.C.   March 27, 1918.


From:  Bureau of Steam Engineering.

To:    Commandant, Fifth Naval District.

Subject:  Listening devices for vessels assigned to Naval Districts.

Reference:  Your letter 18/45 of March 7, 1918.1

     1.  Shipment orders have been prepared for the shipment of the following material to you from Boston, Mass.

              72 “C” Tubes.

              24 Tuned microphone overboard sets.

              24   "       "      drifter sets.

     2.  The above material is for installation on vessels assigned to the Naval District under your command.

     3.  The following extract of a letter from Chief of Naval Operations|2| to Bureau of Steam Engineering is quoted for your information:

“No detectors should be installed on vessels not suitable for, or assigned to, off-shore work. All vessels suitable for listening stations and assigned by the Naval District Commandants to off-shore work, should be fitted with submarine detectors. The Commandants of Naval Districts are best able to select these vessels.

Secrecy regarding equipment while desirable must not be allowed to interfere with actual use of detectors.”

     4.  The overboard “C” tubes are devices for use from a vessel which is stationary in the water and which can have all auxiliary machinery stopped during the time the device is in use. Under ideal conditions the range of this device is equal to that of the tuned microphone and direction can be obtained within about 10 degrees. A listener who from practice becomes expert in the use of the “C” tube, can with very little additional training become an expert listener with all listening devices to be supplied to vessels on distant service.

     5.  The Tuned Microphone Overboard set consists of a tuned microphone with 45 ft. of cable and is for use on drifting vessels having no running auxiliary machinery. This is a non-directional device and while under ideal conditions its range is equal to that of the “C” tube, its range under less favorable conditions is very much greater than the “C” tube.

     6.  The Tuned Microphone Drifter set consists of a tuned microphone with about 300 ft. of cable and necessary floats and sinkers. This device is intended for use from drifting vessels having auxiliary machinery which can not conveniently be stopped. This device does not indicate direction and gives the best results as to range under the least favorable weather conditions.


Assistant to Bureau.   

Source Note: Cy, DNA, RG 45, Entry 520, Box 337. Identification number “E-28-LC” appears in the upper-left corner. A stamp showing the face of a clock appears on the right with the heading “FIFTH NAVAL DISTRICT/COMMANDANT’S OFFICE” and the date list below.

Footnote 1: This document has not been found.

Footnote 2: Adm. William S. Benson.

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