SUBMARINE BELLS TO SONAR & RADAR SUBMARINE SIGNAL COMPANY (1901-1946) Part II

ulPart I of Mr. Merrill’s article appeared in the October 2002 issue of THE SUBMARINE REVIEW.

In the years immediately following the Annistice, many of the various detecting equipments developed during the war years saw continued and broadened use for the next decade. Devices included the previously discussed SC-tubes, Y-tubes, Fessenden 510 Hz oscillators, and the MY-tube. The MY was one of the better multiple carbon button type microphone receiver listening devices developed at the New London Experimental Station. Proposed by Max Mason 3 July 1917, this set permitted the reception of sound waves from a distant source and essentially eliminated the need of using towed devices. By 1929, detectors with improved performance developed by the Sound Division of the Navy Research Laboratory were replacing the SC-tubes with improved performance.

Submarine Signal Company 1920

It was natural that Submarine Signal should continue work related to the detection of sound in the sea. Company assets included 20 years of experience with the submarine bells on a worldwide basis and the extensive WWI manufacture of detection equipment. The Boston-based (Atlantic Avenue) research and manufacturing facilities, 250 employees, and a national and international reputation were further resources of note. The Company also benefited from the experience gained from the Nahant war related detection research.

Synchronous Radio and Underwater Sound signaling

The research staff in 1920 at Submarine Signal developed a radio/underwater sound synchronous system to allow the navigator to determine quickly his distance from an underwater warning bell. With the transmission of a radio signal simultaneously with the bell, the delay time in reception of the bell made it possible to calculate the distance of the ship from the bell. Two years later, a device for receiving returning sound echoes, amplifying them and computing the time interval and distance automatically, appeared.

It should be noted that by 1921 interest in radio beacon warning systems, independent of underwater sound, increased. By 1928, the U.S. Lighthouse Service placed an automatic radio beacon in service.

Sound Division of the Naval Research Laboratory (NRL)

The primary mission of NRL, established in 1923, was to perform applied research to support naval operations. Through the inter-war years, the Sound Division directed by Harvey C. Hayes provided the Navy’s technical leadership in the development of underwater detection systems. The Division primary staff consisted of five engineers and scientists. In addition there were about fifteen NRL support personnel and non-government consultants. This constituted Navy’s sole in-house capability to perform research and development in underwater acoustics until the vast expansion during WWII.

Early in 1922, prior to the move from Annapolis, Dr. Hayes developed a sonic depth finder (SDF). The components consisted of a MY tube (the wartime development by Max Mason at the New London center) as a receiver and a Fessenden oscillator as a signal source and a timing device. This effort initiated by Hayes in developing the first practical sounding instrument was a significant step forward in effectively plotting the ocean depths.

Submarine Signal Company’s Fathometer Depth Sounder

In 1923, Submarine Signal Company introduced the world’s first commercial Fathometer Depth Sounder. It was the first echo sounder to provide accurate, detailed permanent recordings of underwater topography. Based on successful horizontal and vertical sounding experience with the Fessenden oscillator prior to WWI, a successful depth-sounding instrument called Fathometer (registered trademark) was engineered by Submarine Signal Company.

The system included an improved oscillator and other modifications from earlier approaches to depth sounding. Sound waves were transmitted from the oscillator mounted in the ship’s skin. The returning echoes were picked up; and the time interval between each outgoing signal and its returned echo was measured, and converted into distance-depth, and displayed on a calibrated clock-like dial by neon flashes so rapid as to appear essentially continuous. System characteristics accommodated measurement of shallow and deep soundings.

In the decades following WWI, depth sounding and echo ranging evolved side by side. The frequencies used for echo ranging and for depth sounding are distinct and both equipment’s may operate simultaneously. One notable technical difference is the minimum distance requirements. Echo ranging specifies a 50-yard minimum; depth sounding, 4 yards.

Fathometer specifications of the U.S. Hydrographic Office and the Coast and Geodetic Survey required depth measurements to within 5 feet. With sound traveling about 5000 ft/second, time measurement of the order of 1/1000 of a second was essential.

In that era that preceded electronic devices, Submarine Signal Company engineers accomplished precision measurement with accurately-timed electromechanical instrumentation.

Fathometer Users

In 1924, the first commercial Fathometer was installed and tested on Merchants and Miners Transportation Company (M&M) 440 foot liner S.S. BERKSHIRE. A well-witnessed test run of the Fathometer was made from Baltimore, Maryland, to Cape Charles, Virginia. Contours of the ocean floor from 5 to 1500 fathoms were successfully observed with the liner running at full speed. “This Fathometer was demonstrated to the U.S. Navy, U.S. Coast and Geodetic Survey, and U.S. Shipping Board and received their approval for its accuracy and reliability.”42 Installation on some of the ships of the mentioned government activities followed.

The following year, United States Coast and Geodetic Survey (C&GS) obtained a Fathometer designed and built by Submarine Signal Company. C&GS used the model 312 Fathometer primarily for deep-water soundings. With this system, depths were read by noting the position of a continuously rotating white light at the instant the echo was heard in the operator’s headphone. Later, this method was replaced by the red-light method, which utilized a rotating neon tube that flashed adjacent to the depth scale at the arrival time of the echo.

Deep water Fathometer installations were made on the cable-laying ships of All American Cable Incorporated, Mackay, Western Union Cable Telegraph System companies. A May 1925 test of the 1925 Fathometer installation aboard the Western Union Telegraph System cable ship the S.S. CYRUS FIELD prompted its captain, H. H. Bloomer, to write his home office:

“The Fathometer was left running from 6:40 A.M. to 8:00 P.M. Tuesday and gave most accurate results … The distance covered in dense fog was 630 miles and time taken was 62 hours. This was due entirely to the added confidence that the Fathometer gave me and never before have I proceeded with such little anxiety.”

The U.S. Coast and Geodetic Survey installed Fathometers on its oceanographic ships such as the former yacht LYDONIA. With the Fathometers, certain then known and never-before-discovered deeps were sounded. Subsequently, recorded depths ranging from 25,000 to 44,000 feet were found in forty-five locations.

S.S. COLUMBUS

Transoceanic liners were quick to install the Fathometer, often even more than one. German Lloyd’s 2000 passenger liner COLUMBUS the biggest ship in the German merchant fleet made its maiden voyage on April 22, 1924. The liner was to serve the North Atlantic crossing from New York to Bremerhaven. Equipment included the Submarine Signal Fathometer echo sounder.

At that time, because of a suspected depression in the ocean bottom in the vicinity of the Nantucket lightship, there was considerable interest in the topography of the ocean there. Captain Johnson regularly set the Fathometer in operation as the area of interest was approached and took a particularly large number of soundings across this area. With his soundings, Captain Johnson could tell his position accurately in approaching the Nantucket Lightship. In the June 1928 Marine Review, some of his soundings are plotted on a chart and curves drawn to show the topography. The Captain was also the first to adopt the practice on his .. west-ward” course and “eastward” return path (30 miles south) of checking the deep water Fathometer readings with those indicated on the official North Atlantic hydrographic chart.45 In both clement and inclement weather, the Fathometer soundings provided navigational assistance.

V-Class Submarine

The first three submarines of this class were launched in 1924-25 with an additional six more by 1933. A new device installed on V-3 was the electroacoustic Fathometer developed by the Submarine Signal Company. For the first time, it gave the submarine the capability of measuring the depth of water under the keel accurately and instantaneously.

1927

By 1927, a Fathometer recorder was developed that used a stylus to plot and preserve the Fathometer depth readings on charts.47 A new model Fathometer was introduced to meet the needs of small pleasure and commercial boats. In addition to visual depth readings, recorders adapted for four depth-ranges were available for:

• normal needs (in feet and fathoms
• meeting deep-ocean survey measuring (in fathoms)
• shallow-depth harbor and river precision requirements (some versions in inches and others in feet)
• small boat simple inexpensive needs (visual in feet, recording in feet and fathoms

The famous racing schooner ATLANTIC, equipped with a Submarine Signal Fathometer used the device successfully during a New York-to-Bermuda competition event. It was found that even under a 30-40 degree angle of the hull when careening under full sail, visual and recording Fathometer signals were not impaired.

Naval Institute Proceedings February 1943 article “Sonic Sounding” noted ” … by 1929 the U.S. Hydrographic Office was receiving reports of deep-sea sounding daily. At that time, practically all ships had been equipped with sound depth apparatus of the Fessenden type, developed by the Submarine Signal Corporation.”

The Woods Hole Oceanographic Institution (WHOI) Fourth Annual Report of the Director for the year 1933 cited the Submarine Signal Company. “Selecting a fathometer for the research vessel ATLANTIS, after investigating the merits of different types, the “Fathometer” manufactured by the Submarine Signal Company was selected and installed May 1932 on Atlantis … This machine has given satisfaction for soundings as deep as 3000 fathoms.”

A July 25, 1935 accounting of Submarine Signal Company’s Fathometer implementation emphasizes the widespread acceptance of the instrument. At that time, the Fathometer was operating on 649 vessels of various sizes and speeds, and 133 equipments were on order. In the table below, 393 American vessels were equipped and 91 equipments on order for American ships.

Vessels Equipped with the Fathometer

Listening Installation

Late in 1927 Submarine Signal made and installed for the War Department a passive submarine warning system at the approach to New York harbor via the Long Island Sound route. The system was implanted at the east end of Fishers Island off Fort Michie, an outpost of Fort H. G. Wright. Equipment consisted of a 36-spot (microphone) passive listening arrangement. Submarine underwa-ter characteristic hull swishes were detected and the location and moving direction identified.

Echo-Raneing in Post War Period

Developing echo-ranging equipment at this time had the benefit of the hurried WWI submarine detection research as well as real wartime antisubmarine implementation of techniques and strate-gies. Foremost among the wartime efforts was the application of piezoelectric materials as suitable transducer material and in the use of ultrasonic frequencies for detection. These concepts were investigated and demonstrated but not brought to the equipment level during the war years.

Immediately after the war, quartz and Rochelle salt continued to receive attention. Magnetostriction for use as a transducer followed later. However, the level of support and interest in submarine detection research and development lessened. In the mid-I 920s, the Navy was specifying ultrasonic frequencies for accurate short-range detection. System designs stemming from Langevin’s work operated at frequencies of the order of 40 kHz. Earlier Langevin demonstrations witnessed by U.S. Navy ASW officers in October 1918 of equipment aboard a ship at Toulon detecting a submarine created further interest in ultrasonic detec-tion. The demonstration included submarine detection at I 000 and 2000 yards and communication out to 800 yards.49 Additional advantages of working with higher frequencies included avoidance of ocean noise and improved amplification of echoes.

In 1926, a Langevin quartz steel projector was tested in Boston with Langevin in attendance. During the next three years, Subma-rine Signal Company designed; built and tested improved types with quartz steel and magnetostriction projectors. Magnetostriction projectors offered the ability to handle high power without fracturing. Attention during these years was also directed toward developing Rochelle salts transducers.

NRL Sound Division Echo-Ranging Equipment

In the inter-war period regarding equipment, “The Navy equipment was designed by the Bureau of Ships and the Naval Research Laboratory (NRL) and was manufactured by the Subma-rine Signal Co. at an approximate annual rate of 14.

NRL designed and developed a variety of echo-ranging equipments, nearly all operating in the ultrasonic range between 10 and 50 kHz. With bearing and range capability these were an improvement over the earlier acoustic detectors. These experimen-tal systems installed on naval vessels during 1927 had ship speed and range limitations. Later, a series of active sonars involving quartz, Rochelle salt, and magnetostriction transducers evolved from the work at NRL. The principal contractors supporting the Navy Laboratory prior to the WWII years were:

Submarine Signal Echo-Ranging Production

With the Navy building 97 destroyers and 45 submarines during the 1930s, commercial production of some of the Navy-designed detection equipment was assigned to Submarine Signal Company. The Company soon became a significant manufacturer of the Navy’s detection equipment prior to and during WWII. Through 1943, Submarine Signal Company was the dominant supplier of echo sounding and echo ranging to U. S. Navy. Competent naval authority stated that over 90 percent of WWII submarine sinkings involved Submarine Signal Company apparatus.

During the late 1920s and early 1930s NRL developed a series of echo-ranging devices, some of which were in production at Submarine Signal Company by 1933. With continued improve-ments such as streamlined domes, operation at speeds of the order of 15 knots were achieved. These equipments and their variants with suitable adjustments were installed on destroyers and submarines.

QA, the first NRL echo ranging system was completed in 1927. One-mile submarine detection was achieved off Key West, Florida. Eight QA systems were installed on destroyers.52 QB echo-ranging device, Production for submarines of the QB echo-ranging device included 20 at the Washington Navy Yard and 33 at Submarine Signal Company beginning in 1933. Starting in 1934, Submarine Signal QC production was set at six for submarines and six for destroyers each year.

Range, frequency and speed are approximate in the table.

The QC rnagnetostriction system accompanied with Submarine Signal Company NM magnetostriction depth finder was installed in 1933 on the destroyers DEWEY and FARRAGUT. QC systems became the standard on U.S. destroyers during WWII. QB systems with Submarine Signal’s NG depth equipment were installed on submarines CUTTLEFISH and CACHALOT the same year. QC, with a power output of 400 watts, surpassed the lower power capability (20 watts) of the QA and QB systems.

Rochelle Salt crystal echo-ranging device (QB)

About fifty different WWII sonar systems were derived primarily from the QB and QC configurations. QC derivatives appeared in as many as 40 systems. Through 1943, Submarine Signal Company was the only supplier of echo sounding and echo ranging equipment to the United States Navy.

Bathythermograph-Sound Instrumentation

Understanding how the ocean moves and mixes heat requires accurate and continuous measurements of temperature as it changes with depth. Whether sound waves in the water will be bent upwards or downward is a function of the ambient temperatures. In 1936 at MIT, Carl Gustave Rossby and Athelstan Spillhaus developed prototype instrumentation to make temperature depth profiles. Sea tests of the new instrument took place under the aegis of WHOI.

The following year, the device then called bathythennograph (BT) was taken to sea for tests on the WHOl’s research oceano· graphic vessel ATLANTIS with Spillhaus aboard. Initially, a potential user list for the new device consisted of biologists, oceanographers and the fishing industry. Columbus lselin a scientist at WHOI discerned a role for the BT in connection with the underwater detection of submarines.

In late August 1937, the WHOI oceanographic cruise in addition to BT data collection made sound· BT detection tests in conjunction with a U.S. Navy submarine and the destroyer USS SEMMES, a Navy experimental sound vessel attached to the Navy Research Laboratory (NRL). During this cruise, south of Guantanamo Bay, lselin and L. Batchelder of Submarine Signal Company investi· gated a continuing problem of deterioration of sonar range in the afternoon.

Suspicion that the detection equipment operators were at fault was examined. Managing the noontime diets of the operators to maintain peak·operator perfonnance did not prove fruitful, nor did measurements of other ambient parameters and their examination. Extensive collection and examination of sea temperature datas4 led to the realization that temperature gradients in the water where the sound was travelling were responsible. The gradients were either bending the sound wave downward, reducing range, or upward, producing skip. The results were confinned by data collected the following summer. Correlation of “afternoon effect” range reduction and thermoclines became clearer.

The BT provided a practical instrument for quickly gathering this essential ambient information related to sound propagation in seawater and demonstrated the potential importance of the BT in underwater sound detection of submarines and for submarines to avoid detection. The relationship between the thennal layers of seawater and the propagation of sound waves was perceived.

With oceanographic and Navy uses of the BT established, WHOI oceanographer Columbus Iselin consulted Submarine Signal Company’s vice president H.J. W. Fay concerning the manufacture of BTs. Iselin commented on the meeting.

“Mr. Fay is terribly interested in the whole scheme (sic) and has turned over to us the full facilities of their shops and engineering experience.”

“Fay agreed to develop the bathythermograph because his company wished to maintain its long-standing reputation in the ocean instrument field.”

On August 10, 1938, Submarine Signal Company filed for a patent on the BT and began production. The patent was in Spil-haus’s name but Submarine Signal Company received the rights to the design. On May 29, 1941, the U.S. Patent Office applied a secrecy order on the original patent of the bathythermograph because of its importance to the Navy.

War Years

In mid-1940, World War II was nearing the end of its first year. U-boat shipping losses were about 8 ships per month and rapidly increasing to an eventual 143 per month in 1942. Vannevar Bush’s National Defense Research Committee (NDRC) came into being June 27, 1940 with President Franklin D. Roosevelt’s concurrence. This made it possible to broadly pursue efforts to conduct scientific research to create new tools to prosecute the national defense. In regard to the current status of tools for antisubmarine warfare (ASW), it was recognized that they were limited. Supersonic submarine detection equipment worked out to several thousand yards only under favorable conditions.

Coinciding with the start of the NDRC, the Secretary of the Navy asked the National Academy of Sciences (NAS) to advise him on the scientific aspects of the defense against submarines and the adequacy of the Navy’s preparations. E. H. Colpitts, recently retired as vice-president of Bell Telephone Laboratories and World War I submarine detection investigator, led a committee to develop recommendations. For two months, the committee visited Navy ships, shore activities, and the Submarine Signal Company Washington Navy Yard and Submarine Signal were the important builders of the Navy’s submarine detection equipment in 1940.

On January 28, 1941, Colpitt’s recommendations included the need for immediate broad scientific and engineering investigations for the development of equipment and methods involved in submarine and subsurface warfare. Under the auspices ofNDRC, three dominant laboratories were established to enhance the ability to improve the underwater sound aspect of ASW. NDRC contracts with Columbia, Harvard and the University of California resulted in new research laboratories in New London, Connecticut; Cambridge, Massachusetts; and San Diego, California. Further, “Production facilities of the Submarine Signal Co. and Radio Corp. of America were greatly expanded. Other companies such as the Bell Laboratories, the Western Electric Co., and the Bludworth Co., established additional facilities and began supplying sonar’s equipments and accessories.

Radar at Submarine Signal

A 1946 book “Radar’161 in the chapter titled “Who Invented Radar?” lists some American companies active in radar research and development during WWII. The list includes Submarine Signal Company as well as Sperry Gyroscope Company, Bendix Aviation Company, Federal Telephone & Radio Corporation, and others. At Submarine Signal Company, interest in and research for new applications for radio began in 1920 and grew during the 1930s,as shown below by the radio related patents of some of the engineers during this period.

Starting in the 1920s, Submarine Signal research interests moved to radio applications. Initially the research involved paralleling radio use in ways similar to the Company’s applications of underwater sound. An example is the previously-mentioned 1920 synchronizing radio and underwater sound signaling research. Certainly, radar was not anticipated at this early date. By the time of the advent of radar in late 1930s, the acquired competence of the Company’s engineers was a unique asset.

Some Significant Submarine Signal Company Radar Related Patents

R. W. Hart’s pulse-echo radio distance finding system was disclosed to the Navy in 1929 and a patent application submitted. The following year, NRL’s interest in this field increased after a plane flying over Washington, D. C., was detected by radio waves. Submarine Signal, cooperating with NRL, conducted further study of this area of work. In 1933 when Hart’s patent was granted in 1933, the Company was requested by the U.S. Navy to keep the invention .. secret as well as all related future research. ” 63 The Company complied and transferred to the U.S. Government while a number of patent applications were pending. At the same time, the Company refrained from filing relevant foreign applications.

Granting of some of the patents took interesting paths. For example, on June 26, 1942, Submarine Signal Company Engineer B. M. Harrison invented a sonar device and filed for a patent under Public Law 700. It was kept secret for many years. By March 16, 1955, the patent was ready for issue but by that time the patent for an Attack Plotter was allowed for radar as well as sonar.

By the 1939, Submarine Signal radar related advances included:

• Using shorter wavelengths
• Modifying radiating and receiving antennas
• Improving radio beam directivity
• Facilitating the design of keying impulse amplifier
• Developing waveguide phase displacement along acoustic compensator lines

Microwave antenna research by Wilmer L. Barrow and Frank Lewis at MIT by 1939 discussed using directed horns to obtain predictable beam patterns. Further, when two horns were used, isolation between transmitter and receiver was improved. At Submarine Signal, Harold Hart, physicist, was asked to take over the radio echo ranging research and to try to use the new MIT developments.

Hart constructed a radio echo ranging system using a circular sweep cathode ray indicator, a Thyratron modulator and a triode transmitter operating at 50 centimeters. The antenna was a pair of sectored horns manually rotated. These horns were mounted on the roof of the Submarine Signal building on Atlantic Avenue, Boston, and a favorite demonstration was to track the New York boat out of Boston Harbor, after it left its berth across the street.

With the establishment by NDRC of the Radiation Laboratory at MIT November 1940 some members of the new laboratory’s staff visited Submarine Signal for demonstrations of an operating radio echo ranging system. The group included Lee DuBridge, Kenneth Bainbridge, and Louis Turner, all of whom subsequently were to become well known in the radar field through their work at the Radiation Laboratory.

Early in 1942, following the suggestion of BuShips, Submarine Signal began the development order to make ten microwave sets (3000 Meg Hz IO-centimeter S-band) for the Navy. The purpose was the redesign and modification of a Radiation Laboratory experimental radar for manufacture and production. The radar was intended for submarine chasers and motor torpedo boats. Later in the year, Submarine Signal was requested to begin quantity production of the system now designated as the SF radar (in continued cooperation with the Radiation Laboratory). This radar effort was in addition to Submarine Signal’s main sonar production for BuShips.

To comply with the production of radar apparatus, a separate .. Engineering-Manufacturing Division for Radar” was set up, headed by Harold Hart, holder of several radar-related patents. A production of 1200 SF equipment’s followed which found installation on naval coast patrol vessels and mine sweepers. Another radar system, the SU, was manufactured at Submarine Signal. The SU was the first 3 cm 10000 Meg Hz X-band system. This X-band radar was installed on almost 2000 destroyers, LSTs (tank landing ships), scout cruisers, Coast Guard cutters, Maritime Commission vessels, and others.

Some Navy vessels were equipped with Submarine Signal’s three development groups sonar depth, sonar ranging and radar equipment. As of 1955, certain of these systems were still in use by U.S. and Canadian navies.

In the later years of the war, various techniques and devices were secretly developed to counter enemy radar. The area of investigation was referred to as Radar Countermeasures (RCM). Submarine Signal’s contribution was a ship-borne radar direction finder. It was developed in close association with the NRDC Radio Research Laboratory at Harvard. At the time it was the only device capable of intercepting the highest radar frequencies and determining range and bearing of the target radar.

A Company facility was set up in Fall River, Massachusetts to make Mark 15 and 33 fuse time and ballistic computers for naval radar gunfire control along with Fathometers for sonar depth sounding on the Maritime Commission vessels.

Submarine Signal Division (Raytheon)

In 1946, the year after the end of World War II, Submarine Signal Company completed 45 years of important participation in the evolving field of underwater detection. It was known in the commercial world for its Fathometer and the wartime manufacture of sonar and radar systems was substantial. .. Its wartime sales had grown to over $50 million dollars a year; its profits hit a peak of $1. 7 million.”

As mentioned above, the Company’s work in the preceding decade and during WWII was classified and consequently not in the purview of the commercial world. The U.S. Navy was its largest and most important customer. Other developmental projects involved Carnegie Institution and other selected screened and discrete groups. This limited customer base did not enhance Submarine Signal’s position in the commercial world. With the war’s end and reduced spending by government agencies, this position was not a totally favorable one.

From 1925, in parallel with Submarine Signal’s growth in Boston’s emerging electronics industries, Raytheon grew and expanded at a greater rate. During the late 1920s and 30s, Raythe-on inserted itself in an important role in the development and manufacture of radio tubes, an essential part of the expansion of commercial radio and radio receivers. Raytheon, with commercial products, was nationally known. The war years’ radio tubes, radar, and other defense systems provided opportunities for growth and 1945 saw a fiscal wartime high for Raytheon of more than $17 4 million in sales. Through the years, Submarine Signal bought millions of dollars of Raytheon’s radio tubes and components. The two companies one large and one small shared advanced research projects and were well known to each other in the Boston community.

Through its first twenty years, Raytheon grew in part by careful acquisition of industrial activities engaged in making products that related to or directly supported Raytheon’s product line. Further, Harvard, MIT, and Tufts science and engineering staffs and students had a presence in Raytheon as consultants and graduates as engineers. These same schools and their staffs were known to Submarine Signal.

It may be assumed that with materially reduced defense spending in 1946 and Submarine Signal’s modest commercial base, acquisition of Submarine Signal by Raytheon could have advantages for each company. From the Raytheon viewpoint, significant sonar and underwater sound capability would be added. Submarine Signal’s radar R&D and manufacturing experience would also augment Raytheon’s. On May 26, 1946, Submarine Signal became a division of Raytheon.

2002-Heritage of Submarine Signal

Submarine Signal’s underwater acoustics scientists and engineers retained their own organization at Raytheon’s Newton and Wayland, Massachusetts laboratories. New submarine and destroyer sonar systems evolved, as well as active ASW helicopter equipment.

By 1960, the Submarine Signal group then a division of Raytheon was located in a new advanced industrial ASW center at Portsmouth, Rhode Island. This action was in response to the changes in ASW precipitated with the advent of the nuclear submarine and submarine-launched missiles.

The continuing research and system development tradition stemming from Submarine Signal in the new century carries the Raytheon designation Integrated Defense Systems. U.S. Navy systems include surface ship self defense, submarine combat control for current attack submarines, system integration for amphibious assault craft and Marine command and control needs. Military vessels of Turkey, United Kingdom, and Italy are also users of the Raytheon Integrated Defense Systems group.