bottom. The four-inch thick transducer consisted of quartz slabs sandwiched between steel discs 
about sixteen inches in diameter. It “pinged” out 1/4 second pulses of energy which traveled hori- 
zontally in a cone-shaped path. When part of the sound wave struck the target | Submarine, a small 
portion of the energy was reflected back to the transducer which fed the “echo” through an elec- 
tronic amplifier to earphones and a range (distance) indicator. The direction in which the trans- 
ducer was facing indicated the target s bearing. Only about twenty watts of power was transferred 
to the water and echoes were obtained from a few hundred feet distance. The equipment gave re- 
Sults while the ship in which it was installed was underway at speeds below 3 or 4 knots, and in 
1927 several Naval vessels commenced sea trials with the NRL quartz-steel echo ranging Sonar. 
These echo ranging inventions are considered the greatest contributions to the science of under- 
water detection. 
About 1927 the Submarine Signal Company was producing water depth indicators called 
“Fathometers’. The transmitter consisted of an electro-magnet which banged a piston against 
a diaphram facing the ocean bottom thereby emitting a 1000 cycle sound wave which was reflected 
from the ocean bottom to a button type microphone. This “echo” was fed to a calibrated scale 
where neon light flashes indicated the depth. Fathometers were eventually installed in most Naval 
vessels. 
By 1929 NRL had produced a listening Sonar which replaced the acoustical SC tubes in sub- 
marines. It was designated as JK and was in effect the listening portion of our echo ranging Sonar; 
thus, the listening head had the shape of current transducers, but in place of the quartz crystals 
used in echo ranging, the newly developed Rochelle Salt Crystals were employed Since they were 
comparatively more sensitive. The Navy Yard at Washington produced the JK’s for all the sub- 
marines we then had. The transducer was mounted on the top side thereby permitting use of the 
Sonar only when the Submarines submerged. The JK increased listening ranges to about 5 miles 
under average water conditions and gave bearings accurate to within a few degrees. Shortly 
afterwards they were modified by addition of a small transmitter which provided a feature simi- 
lar to the “ping feature jin echo ranging; this feature was used for communication between sub- 
marines. Also, a few JK’s were modified for underwater voice communication. For many years 
the JK remained as the most valuable listening equipment in submarines. 
About 1931 NRL developed the QB echo ranging Sonar for submarines. It was practically 
identical to our surface vessel Sonar except that it employed Rochelle Salt Crystals instead of the 
quartz crystals used in surface ship transducers. The QB’s (in addition to the JK’s) were sub- 
Sequently installed in new construction submarines where the transducer protruded through the 
keel, thereby enabling use of the QB whether the submarines were surfaced or submerged. 
Thus by 1933 the Navy Yard at Washington had produced about a score of quartz-steel echo 
ranging for destroyers and was engaged in production of ‘about 60 JK listening Sonar for sub- 
marines, and the Submarine Signal Company commenced production of about 30 QB echo ranging 
Sonar for Submarines. These equipments operated satisfactorily up to ship speeds of about 5 
knots beyond which the roar and crackle of water noises drowned out target noises and echoes, 
To reduce the turbulence caused by the movement of the flatfaced transducer through the water, 
NRL produced a spherical cover about 19 inches in diameter, made of sound transparent rubber 
developed in collaboration with the Goodrich Company. This “dome” permitted 10 knot speeds 
before water noises became excessive, and was subsequently incorporated in all our transducers. 
About this time a transducer was invented in which magneto-striction tubes replaced the 
quartz or Salt crystals. These tubes were small electromagnets consisting of a 3 inch long - 3/8 
inch diameter nickel alloy hollow tube, around which was wound a coil of wire. The tubes elon- 
gated or contracted when their magnetic flux was changed. The electrical energy from the trans- 
mitter caused movements of the ma eto-striction tubes which resulted in vibrating the diaphram 
of the transducer, thereby emitting pings” . Conversely, when any sound waves which struck the 
diaphram caused a change in the magnetic flux of the magneto-striction tubes, an electric cur- 
rent was generated which resulted in signals corresponding to the sound source, i.e., propeller 
noises, echoes from pings, etc. In 1934 the Bureau of Ships designed, and the Submarine Signal 
Company commenced production of, the magneto-striction echo ranging equipment which were 
subsequently installed in 8 destroyers and 6 submarines per year. The Submarine Signal 
osio a-2405 
