De 
LIST OF ILLUSTRATIONS 
ILLUSTRATION A. 
FIRST NAVY SONAR - World War I complete SC listening apparatus. Water 
sounds activate 3 inch diameter rubber balls which transfer sounds thru air 
filled acoustic piping to stethoscope, worn by operator, who centers sound 
pinaurally by turning handle neer (12). Pointer on calibrated scale near (9) 
_ indicates direction of target. No provisions for obtaining target's distance. 
"T" shaped SC tubes were hung overside or protruded thru bottom of Subchasers. 
ILLUSTRATION 8B. 
SHIP CROSS SECTION SHOWS SONAR EQUIPMENT - This cross section of a combat 
ship shows Sonar Equipment installations, both in the pilot house or control 
room, above, and below, in the lower sound room, in which the retractable gear 
and dome is located. 
ILLUSTRATION C. 
MODERN SUBMARINE LISTENING SONAR - Model "JP" listening equipment. Top- 
side hydrophone consists of 3-foot long magneto-striction tube (electro-magnet). 
Sound waves striking the tube cause a change in its magnetic flux thereby 
generating a current which results in signals corresponding to the sound source, 
i. e., propel’er noise, etc. JP has good directional accuracy on sounds up to 
about 10 miles distant in good water conditions. 
ILLUSTRATION D. 
‘ 
RADIO-SONO BUOY EMPLOYMENT - Patrol plane gets pip on its Radar from U-boat 
Several miles distance. U-boat hears Radar or sees plane and submerges. Plane 
parachutes Radio-Sono Buoy Which floats, lets: out Sonar hydrophone below weters 
surface and has Radio antennae above water. Hydrophone detects sound waves creat- 
ed by U-boat, transfers sounds to Radio which transmits them to patrol plane. 
Depth charges may be dropped by plane. Several more buoys maybe perachuted in 
order to maintain contact with U-boat. Plane calls surface ship which uses echo- 
ranging Sonar to accurately locate and attack U-boat. 
ILLUSTRATION E. 
ECHO RANGING INSTALLATION IN MODERN SUBMARINE - The six panels constitute 
the "Sonar Stack" which embody the power controls, the “Driver” which energizes 
the Transducer, the Receiver-Amplifier and its controls, the range and bearing 
indicators, etc. The two pillars at the left are the "Train-Hoist"” control for 
the dome which may be retracted into the Submarine. The Transducer is inside 
the dome and may be rotated to any bearing desired. 
ILLUSTRATION F. 
SONAR GOERS -A- FISHING - This shark got too nosey and was hooked on an 
escort vessel's Sonar dome while at sea and stayed hooked till the ship was 
drydocked,. Ships with faulty Sonar were not very useful as escorts, usuaily 
dropped out of convoy duty, and put in at one of the many bases for repairs. 
Necessary repair parts were often flown in order to have every available Sonar 
equipped vessel at sea. 
