RS-422 known as TIA/EIA-422, is a technical standard originated by the Electronic Industries Alliance that specifies electrical characteristics of a digital signaling circuit. Differential signaling can transmit data at rates as high as 10 Mbit/s, or may be sent on cables as long as 1,500 meters; some systems directly interconnect using RS-422 signals, or RS-422 converters may be used to extend the range of RS-232 connections. The standard only defines signal levels. RS-422 is the common short form title of American National Standards Institute standard ANSI/TIA/EIA-422-B Electrical Characteristics of Balanced Voltage Differential Interface Circuits and its international equivalent ITU-T Recommendation T-REC-V.11 known as X.27. These technical standards specify the electrical characteristics of the balanced voltage digital interface circuit. RS-422 provides for data transmission, using balanced, or differential, with unidirectional/non-reversible, terminated or non-terminated transmission lines, point to point, or multi-drop.
In contrast to EIA-485, RS-422/V.11 does not allow multiple drivers but only multiple receivers. Revision B, published in May 1994 was reaffirmed by the Telecommunications Industry Association in 2005. Several key advantages offered by this standard include the differential receiver, a differential driver and data rates as high as 10 Megabits per second at 12 meters. Since the signal quality degrades with cable length, the maximum data rate decreases as cable length increases. Figure A.1 in the annex plotting this stops at 10 Mbit/s. The maximum cable length is not specified in the standard. Limitations on line length and data rate varies with the parameters of the cable length and termination, as well as the individual installation. Figure A.1 shows a maximum length of 1200 meters, but this is with a termination and the annex discusses the fact that many applications can tolerate greater timing and amplitude distortion, that experience has shown that the cable length may be extended to several kilometers.
Conservative maximum data rates with 24AWG UTP cable are 10 Mbit/s at 12 m to 90 kbit/s at 1200 m as shown in the figure A.1. This figure is a conservative guide based on empirical data, not a limit imposed by the standard. RS-422 specifies the electrical characteristics of a single balanced signal; the standard was written to be referenced by other standards that specify the complete DTE/DCE interface for applications which require a balanced voltage circuit to transmit data. These other standards would define protocols, pin assignments and functions. Standards such as EIA-530 and EIA-449 use RS-422 electrical signals; some RS-422 devices have 4 screw terminals for pairs of wire, with one pair used for data in each direction. RS-422 cannot implement a true multi-point communications network such as with EIA-485 since there can be only one driver on each pair of wires; however one driver can fan-out to up to ten receivers. RS-422 can interoperate with interfaces designed to MIL-STD-188-114B. RS-422 uses a nominal 0 to 5 volt signal while MIL-STD-188-114B uses a signal symmetric about 0 V.
However the tolerance for common mode voltage in both specifications allows them to interoperate. Care must be taken with the termination network. EIA-423 is a similar specification for unbalanced signaling; when used in relation to communications wiring, RS-422 wiring refers to cable made of 2 sets of twisted pair with each pair being shielded, a ground wire. While a double pair cable may be practical for many RS-422 applications, the RS-422 specification only defines one signal path and does not assign any function to it. Any complete cable assembly with connectors should be labeled with the specification that defined the signal function and mechanical layout of the connector, such as RS-449; the most widespread use of RS-422 was on the early Macintosh computers. This was implemented in a multi-pin connector that had enough pins to support the majority of the common RS-232 pins; the ports could be put into either RS-232 or RS-422 mode, which changed the behavior of some of the pins while turning others on or off completely.
These connectors were used both to support RS-232 devices like modems, as well as AppleTalk networking, RS-422 printers, other peripherals. Two such ports were part of every Mac until they were replaced, along with ADB ports, by Universal Serial Bus on the iMac in 1998. RS-422 is a common transport mechanism for RS-232 extenders; these consist of RS-232 ports on either end of an RS-422 connection. Before hard disk based playout and editing systems were used, Broadcast automation systems and post-production linear editing facilities used RS-422A to remotely control the players/recorders located in the central apparatus room. In most cases the Sony 9-pin connection was used; this is the de facto industry standard connector for RS-422, still found on much broadcast equipment today. Electronic Industries Alliance Profibus Fieldbus List of network buses This article is based on material taken from the Free On-line Dictionary of Computing prior to 1 November 2008 and incorporated under the "relicensing" terms of the GFDL, version 1.3 or later.
The Telecommunications Industry Association National Semiconductor Application Note AN-1031 "TIA/EIA-422-B Overview", January 2000, Nation
Telecommunication is the transmission of signs, messages, writings and sounds or information of any nature by wire, optical or other electromagnetic systems. Telecommunication occurs when the exchange of information between communication participants includes the use of technology, it is transmitted either electrically over physical media, such as cables, or via electromagnetic radiation. Such transmission paths are divided into communication channels which afford the advantages of multiplexing. Since the Latin term communicatio is considered the social process of information exchange, the term telecommunications is used in its plural form because it involves many different technologies. Early means of communicating over a distance included visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, optical heliographs. Other examples of pre-modern long-distance communication included audio messages such as coded drumbeats, lung-blown horns, loud whistles. 20th- and 21st-century technologies for long-distance communication involve electrical and electromagnetic technologies, such as telegraph and teleprinter, radio, microwave transmission, fiber optics, communications satellites.
A revolution in wireless communication began in the first decade of the 20th century with the pioneering developments in radio communications by Guglielmo Marconi, who won the Nobel Prize in Physics in 1909, other notable pioneering inventors and developers in the field of electrical and electronic telecommunications. These included Charles Wheatstone and Samuel Morse, Alexander Graham Bell, Edwin Armstrong and Lee de Forest, as well as Vladimir K. Zworykin, John Logie Baird and Philo Farnsworth; the word telecommunication is a compound of the Greek prefix tele, meaning distant, far off, or afar, the Latin communicare, meaning to share. Its modern use is adapted from the French, because its written use was recorded in 1904 by the French engineer and novelist Édouard Estaunié. Communication was first used as an English word in the late 14th century, it comes from Old French comunicacion, from Latin communicationem, noun of action from past participle stem of communicare "to share, divide out.
Homing pigeons have been used throughout history by different cultures. Pigeon post had Persian roots, was used by the Romans to aid their military. Frontinus said; the Greeks conveyed the names of the victors at the Olympic Games to various cities using homing pigeons. In the early 19th century, the Dutch government used the system in Sumatra, and in 1849, Paul Julius Reuter started a pigeon service to fly stock prices between Aachen and Brussels, a service that operated for a year until the gap in the telegraph link was closed. In the Middle Ages, chains of beacons were used on hilltops as a means of relaying a signal. Beacon chains suffered the drawback that they could only pass a single bit of information, so the meaning of the message such as "the enemy has been sighted" had to be agreed upon in advance. One notable instance of their use was during the Spanish Armada, when a beacon chain relayed a signal from Plymouth to London. In 1792, Claude Chappe, a French engineer, built the first fixed visual telegraphy system between Lille and Paris.
However semaphore suffered from the need for skilled operators and expensive towers at intervals of ten to thirty kilometres. As a result of competition from the electrical telegraph, the last commercial line was abandoned in 1880. On 25 July 1837 the first commercial electrical telegraph was demonstrated by English inventor Sir William Fothergill Cooke, English scientist Sir Charles Wheatstone. Both inventors viewed their device as "an improvement to the electromagnetic telegraph" not as a new device. Samuel Morse independently developed a version of the electrical telegraph that he unsuccessfully demonstrated on 2 September 1837, his code was an important advance over Wheatstone's signaling method. The first transatlantic telegraph cable was completed on 27 July 1866, allowing transatlantic telecommunication for the first time; the conventional telephone was invented independently by Alexander Bell and Elisha Gray in 1876. Antonio Meucci invented the first device that allowed the electrical transmission of voice over a line in 1849.
However Meucci's device was of little practical value because it relied upon the electrophonic effect and thus required users to place the receiver in their mouth to "hear" what was being said. The first commercial telephone services were set-up in 1878 and 1879 on both sides of the Atlantic in the cities of New Haven and London. Starting in 1894, Italian inventor Guglielmo Marconi began developing a wireless communication using the newly discovered phenomenon of radio waves, showing by 1901 that they could be transmitted across the Atlantic Ocean; this was the start of wireless telegraphy by radio. Voice and music had little early success. World War I accelerated the development of radio for military communications. After the war, commercial radio AM broadcasting began in the 1920s and became an important mass medium for entertainment and news. World War II again accelerated development of radio for the wartime purposes of aircraft and land communication, radio navigation and radar. Development of stereo FM broadcasting of radio
Tactical data link
A tactical data link uses a data link standard in order to provide communication via radio waves or cable used by the U. S. armed forces and NATO nations. All military C3 systems use standardized TDL to transmit and receive tactical data. Multi-TDL network refers to the network of similar and dissimilar TDLs integrated through gateways and correlators to bring the common tactical picture and/or common operational picture together; the term tactical digital information link was made obsolete and is now more seen as tactical data link. TDLs are characterized by their standard transmission formats; this is written as <Message Format>/<Transmission Format>. In NATO, tactical data link standards are being developed by the Data Link Working Group of the Information Systems Sub-Committee in line with the appropriate STANAG. In NATO, there exist tactical data link standards as follows: BACN Global Information Grid Inter/Intra Flight Data Link JREAP MANDRIL Multifunction Advanced Data Link Network emulation for simulation / emulation of tactical data links SIMPLE Tactical Common Data Link Federation of American Scientists TDL information page This article was based on public domain text from Army Airspace Command and Control in a Combat Zone, Department of the Army, publication FM 3-52, August 2002
The North Atlantic Treaty Organization called the North Atlantic Alliance, is an intergovernmental military alliance between 29 North American and European countries. The organization implements the North Atlantic Treaty, signed on 4 April 1949. NATO constitutes a system of collective defence whereby its independent member states agree to mutual defence in response to an attack by any external party. NATO's Headquarters are located in Haren, Belgium, while the headquarters of Allied Command Operations is near Mons, Belgium. Since its founding, the admission of new member states has increased the alliance from the original 12 countries to 29; the most recent member state to be added to NATO is Montenegro on 5 June 2017. NATO recognizes Bosnia and Herzegovina, North Macedonia and Ukraine as aspiring members. An additional 21 countries participate in NATO's Partnership for Peace program, with 15 other countries involved in institutionalized dialogue programs; the combined military spending of all NATO members constitutes over 70% of the global total.
Members have committed to reach or maintain defense spending of at least 2% of GDP by 2024. On 4 March 1947 the Treaty of Dunkirk was signed by France and the United Kingdom as a Treaty of Alliance and Mutual Assistance in the event of a possible attack by Germany or the Soviet Union in the aftermath of World War II. In 1948, this alliance was expanded to include the Benelux countries, in the form of the Western Union referred to as the Brussels Treaty Organization, established by the Treaty of Brussels. Talks for a new military alliance which could include North America resulted in the signature of the North Atlantic Treaty on 4 April 1949 by the member states of the Western Union plus the United States, Portugal, Norway and Iceland; the North Atlantic Treaty was dormant until the Korean War initiated the establishment of NATO to implement it, by means of an integrated military structure: This included the formation of Supreme Headquarters Allied Powers Europe in 1951, which adopted the Western Union's military structures and plans.
In 1952 the post of Secretary General of NATO was established as the organization's chief civilian. That year saw the first major NATO maritime exercises, Exercise Mainbrace and the accession of Greece and Turkey to the organization. Following the London and Paris Conferences, West Germany was permitted to rearm militarily, as they joined NATO in May 1955, in turn a major factor in the creation of the Soviet-dominated Warsaw Pact, delineating the two opposing sides of the Cold War. Doubts over the strength of the relationship between the European states and the United States ebbed and flowed, along with doubts over the credibility of the NATO defense against a prospective Soviet invasion – doubts that led to the development of the independent French nuclear deterrent and the withdrawal of France from NATO's military structure in 1966. In 1982 the newly democratic Spain joined the alliance; the collapse of the Warsaw Pact in 1989–1991 removed the de facto main adversary of NATO and caused a strategic re-evaluation of NATO's purpose, nature and focus on the continent of Europe.
This shift started with the 1990 signing in Paris of the Treaty on Conventional Armed Forces in Europe between NATO and the Soviet Union, which mandated specific military reductions across the continent that continued after the dissolution of the Soviet Union in December 1991. At that time, European countries accounted for 34 percent of NATO's military spending. NATO began a gradual expansion to include newly autonomous Central and Eastern European nations, extended its activities into political and humanitarian situations that had not been NATO concerns. After the fall of the Berlin Wall in Germany in 1989, the organization conducted its first military interventions in Bosnia from 1992 to 1995 and Yugoslavia in 1999 during the breakup of Yugoslavia. Politically, the organization sought better relations with former Warsaw Pact countries, most of which joined the alliance in 1999 and 2004. Article 5 of the North Atlantic treaty, requiring member states to come to the aid of any member state subject to an armed attack, was invoked for the first and only time after the September 11 attacks, after which troops were deployed to Afghanistan under the NATO-led ISAF.
The organization has operated a range of additional roles since including sending trainers to Iraq, assisting in counter-piracy operations and in 2011 enforcing a no-fly zone over Libya in accordance with UN Security Council Resolution 1973. The less potent Article 4, which invokes consultation among NATO members, has been invoked five times following incidents in the Iraq War, Syrian Civil War, annexation of Crimea; the first post-Cold War expansion of NATO came with German reunification on 3 October 1990, when the former East Germany became part of the Federal Republic of Germany and the alliance. As part of post-Cold War restructuring, NATO's military structure was cut back and reorganized, with new forces such as the Headquarters Allied Command Europe Rapid Reaction Corps established; the changes brought about by the collapse of the Soviet Union on the military balance in Europe were recognized in the Adapted Conventional Armed Forces in Europe Treaty, signed in 1999. The policies of French President Nicolas Sarkozy resulted in a major reform of France's military position, culminating with the return to full membership on 4 April 2009, which included France rejoining the NATO Military Command Structure, while maintaining an independent nuclear deterrent.
Between 1994 and 1997, wider forums for regional co
Interoperability is a characteristic of a product or system, whose interfaces are understood, to work with other products or systems, at present or in the future, in either implementation or access, without any restrictions. While the term was defined for information technology or systems engineering services to allow for information exchange, a broader definition takes into account social and organizational factors that impact system to system performance. Task of building coherent services for users when the individual components are technically different and managed by different organizations If two or more systems are capable of communicating with each other, they exhibit syntactic interoperability when using specified data formats and communication protocols. XML or SQL standards are among the tools of syntactic interoperability; this is true for lower-level data formats, such as ensuring alphabetical characters are stored in a same variation of ASCII or a Unicode format in all the communicating systems.
Beyond the ability of two or more computer systems to exchange information, semantic interoperability is the ability to automatically interpret the information exchanged meaningfully and in order to produce useful results as defined by the end users of both systems. To achieve semantic interoperability, both sides must refer to a common information exchange reference model; the content of the information exchange requests are unambiguously defined: what is sent is the same as what is understood. The possibility of promoting this result by user-driven convergence of disparate interpretations of the same information has been object of study by research prototypes such as S3DB. Cross-domain interoperability involves multiple social, political, legal entities working together for a common interest and/or information exchange. Interoperability imply Open standards ab-initio, i.e. by definition. Interoperability imply exchanges between a range of products, or similar products from several different vendors, or between past and future revisions of the same product.
Interoperability may be developed post-facto, as a special measure between two products, while excluding the rest, by using Open standards. When a vendor is forced to adapt its system to a dominant system, not based on Open standards, it is not interoperability but only compatibility. Open standards rely on a broadly consultative and inclusive group including representatives from vendors and others holding a stake in the development that discusses and debates the technical and economic merits and feasibility of a proposed common protocol. After the doubts and reservations of all members are addressed, the resulting common document is endorsed as a common standard; this document is subsequently released to the public, henceforth becomes an open standard. It is published and is available or at a nominal cost to any and all comers, with no further encumbrances. Various vendors and individuals can use the standards document to make products that implement the common protocol defined in the standard, are thus interoperable by design, with no specific liability or advantage for any customer for choosing one product over another on the basis of standardised features.
The vendors' products compete on the quality of their implementation, user interface, ease of use, price, a host of other factors, while keeping the customers data intact and transferable if he chooses to switch to another competing product for business reasons. Post facto interoperability may be the result of the absolute market dominance of a particular product in contravention of any applicable standards, or if any effective standards were not present at the time of that product's introduction; the vendor behind that product can choose to ignore any forthcoming standards and not co-operate in any standardisation process at all, using its near-monopoly to insist that its product sets the de facto standard by its market dominance. This is not a problem if the product's implementation is open and minimally encumbered, but it may as well be both closed and encumbered; because of the network effect, achieving interoperability with such a product is both critical for any other vendor if it wishes to remain relevant in the market, difficult to accomplish because of lack of co-operation on equal terms with the original vendor, who may well see the new vendor as a potential competitor and threat.
The newer implementations rely on clean-room reverse engineering in the absence of technical data to achieve interoperability. The original vendors can provide such technical data to others in the name of'encouraging competition,' but such data is invariably encumbered, may be of limited use. Availability of such data is not equivalent to an open standard, because: The data is provided by the original vendor on a discretionary basis, who has every interest in blocking the effective implementation of competing solutions, may subtly alter or change its product in newer revisions, so that competitors' implementations are but not quite interoperable, leading customers to consider them unreliable or of a lower quality; these changes can either not be passed on to other vendors at all, or passed on after a strategic delay, maintaining the market dominance of the original vendor. The data itself may be encumbered, e.g. by patents or pricing, leading to a dependence of all competing solutions on the original vendor, leading a revenue stream from the competitors' customers back to the original vendor.
This revenue stream is only a result of the origina
JPEG is a used method of lossy compression for digital images for those images produced by digital photography. The degree of compression can be adjusted, allowing a selectable tradeoff between storage size and image quality. JPEG achieves 10:1 compression with little perceptible loss in image quality. JPEG compression is used in a number of image file formats. JPEG/Exif is the most common image format used by digital cameras and other photographic image capture devices; these format variations are not distinguished, are called JPEG. The term "JPEG" is an initialism/acronym for the Joint Photographic Experts Group, which created the standard; the MIME media type for JPEG is image/jpeg, except in older Internet Explorer versions, which provides a MIME type of image/pjpeg when uploading JPEG images. JPEG files have a filename extension of.jpg or.jpeg. JPEG/JFIF supports a maximum image size of 65,535×65,535 pixels, hence up to 4 gigapixels for an aspect ratio of 1:1. "JPEG" stands for Joint Photographic Experts Group, the name of the committee that created the JPEG standard and other still picture coding standards.
The "Joint" stood for ISO TC97 WG8 and CCITT SGVIII. In 1987, ISO TC 97 became ISO/IEC JTC1 and, in 1992, CCITT became ITU-T. On the JTC1 side, JPEG is one of two sub-groups of ISO/IEC Joint Technical Committee 1, Subcommittee 29, Working Group 1 – titled as Coding of still pictures. On the ITU-T side, ITU-T SG16 is the respective body; the original JPEG Group was organized in 1986, issuing the first JPEG standard in 1992, approved in September 1992 as ITU-T Recommendation T.81 and, in 1994, as ISO/IEC 10918-1. The JPEG standard specifies the codec, which defines how an image is compressed into a stream of bytes and decompressed back into an image, but not the file format used to contain that stream; the Exif and JFIF standards define the used file formats for interchange of JPEG-compressed images. JPEG standards are formally named as Information technology – Digital compression and coding of continuous-tone still images. ISO/IEC 10918 consists of the following parts: Ecma International TR/98 specifies the JPEG File Interchange Format.
The JPEG compression algorithm operates at its best on photographs and paintings of realistic scenes with smooth variations of tone and color. For web usage, where reducing the amount of data used for an image is important for responsive presentation, JPEG's compression benefits make JPEG popular. JPEG/Exif is the most common format saved by digital cameras. However, JPEG is not well suited for line drawings and other textual or iconic graphics, where the sharp contrasts between adjacent pixels can cause noticeable artifacts; such images are better saved in a lossless graphics format such as TIFF, GIF, PNG, or a raw image format. The JPEG standard includes a lossless coding mode; as the typical use of JPEG is a lossy compression method, which reduces the image fidelity, it is inappropriate for exact reproduction of imaging data. JPEG is not well suited to files that will undergo multiple edits, as some image quality is lost each time the image is recompressed if the image is cropped or shifted, or if encoding parameters are changed – see digital generation loss for details.
To prevent image information loss during sequential and repetitive editing, the first edit can be saved in a lossless format, subsequently edited in that format finally published as JPEG for distribution. JPEG uses a lossy form of compression based on the discrete cosine transform; this mathematical operation converts each frame/field of the video source from the spatial domain into the frequency domain. A perceptual model based loosely on the human psychovisual system discards high-frequency information, i.e. sharp transitions in intensity, color hue. In the transform domain, the process of reducing information is called quantization. In simpler terms, quantization is a method for optimally reducing a large number scale into a smaller one, the transform-domain is a convenient representation of the image because the high-frequency coefficients, which contribute less to the overall picture than other coefficients, are characteristically small-values with high compressibility; the quantized coefficients are sequenced and losslessly packed into the output bitstream.
Nearly all software implementations of JPEG permit user control over the compression ratio, allowing the user to trade off picture-quality for smaller file size. In embedded applications, the parameters are fixed for the application; the compression method is lossy, meaning that some original image information is lost and cannot be restored affecting image quality. There is an optional lossless mode defined in the JPEG standard. However, this mode is not supported in products. There is an interlaced progressive JPEG format, in which data is compressed in multiple passes of progressively higher detail; this is ideal for large images that will be displayed while downloading over a slow connection, allowing a reasonable preview after receiving only a portion of the data. However, support for progressive JPEGs is not universal; when progressive JPEGs are received by programs that do not support them (such
United States Department of Defense
The Department of Defense is an executive branch department of the federal government charged with coordinating and supervising all agencies and functions of the government concerned directly with national security and the United States Armed Forces. The department is the largest employer in the world, with nearly 1.3 million active duty servicemen and women as of 2016. Adding to its employees are over 826,000 National Guardsmen and Reservists from the four services, over 732,000 civilians bringing the total to over 2.8 million employees. Headquartered at the Pentagon in Arlington, just outside Washington, D. C. the DoD's stated mission is to provide "the military forces needed to deter war and ensure our nation's security". The Department of Defense is headed by the Secretary of Defense, a cabinet-level head who reports directly to the President of the United States. Beneath the Department of Defense are three subordinate military departments: the United States Department of the Army, the United States Department of the Navy, the United States Department of the Air Force.
In addition, four national intelligence services are subordinate to the Department of Defense: the Defense Intelligence Agency, the National Security Agency, the National Geospatial-Intelligence Agency, the National Reconnaissance Office. Other Defense Agencies include the Defense Advanced Research Projects Agency, the Defense Logistics Agency, the Missile Defense Agency, the Defense Health Agency, Defense Threat Reduction Agency, the Defense Security Service, the Pentagon Force Protection Agency, all of which are under the command of the Secretary of Defense. Additionally, the Defense Contract Management Agency provides acquisition insight that matters, by delivering actionable acquisition intelligence from factory floor to the warfighter. Military operations are managed by ten functional Unified combatant commands; the Department of Defense operates several joint services schools, including the Eisenhower School and the National War College. The history of the defense of the United States started with the Continental Congress in 1775.
The creation of the United States Army was enacted on 14 June 1775. This coincides with the American holiday Flag Day; the Second Continental Congress would charter the United States Navy, on 13 October 1775, create the United States Marine Corps on 10 November 1775. The Preamble of the United States Constitution gave the authority to the federal government to defend its citizens: We the People of the United States, in Order to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defence, promote the general Welfare, secure the Blessings of Liberty to ourselves and our Posterity, do ordain and establish this Constitution for the United States of America. Upon the seating of the first Congress on 4 March 1789, legislation to create a military defense force stagnated as they focused on other concerns relevant to setting up the new government. President George Washington went to Congress to remind them of their duty to establish a military twice during this time.
On the last day of the session, 29 September 1789, Congress created the War Department, historic forerunner of the Department of Defense. The War Department handled naval affairs until Congress created the Navy Department in 1798; the secretaries of each of these departments reported directly to the president as cabinet-level advisors until 1949, when all military departments became subordinate to the Secretary of Defense. After the end of World War II, President Harry Truman proposed creation of a unified department of national defense. In a special message to Congress on 19 December 1945, the President cited both wasteful military spending and inter-departmental conflicts. Deliberations in Congress went on for months focusing on the role of the military in society and the threat of granting too much military power to the executive. On 26 July 1947, Truman signed the National Security Act of 1947, which set up a unified military command known as the "National Military Establishment", as well as creating the Central Intelligence Agency, the National Security Council, National Security Resources Board, United States Air Force and the Joint Chiefs of Staff.
The act placed the National Military Establishment under the control of a single Secretary of Defense. The National Military Establishment formally began operations on 18 September, the day after the Senate confirmed James V. Forrestal as the first Secretary of Defense; the National Military Establishment was renamed the "Department of Defense" on 10 August 1949 and absorbed the three cabinet-level military departments, in an amendment to the original 1947 law. Under the Department of Defense Reorganization Act of 1958, channels of authority within the department were streamlined, while still maintaining the ordinary authority of the Military Departments to organize and equip their associated forces; the Act clarified the overall decision-making authority of the Secretary of Defense with respect to these subordinate Military Departments and more defined the operational chain of command over U. S. military forces as running from the president to the Secretary of Defense and to the unified combatant commanders.
Provided in this legislation was a centralized research authority, the Advanced Research Projects Agency known as DARPA. The act was written and promoted by the Eisenhower administration, was signed into law 6 August 1958; the Secretary of Defense, appointed by the president with the advice and consent of the Senate, is by federal law (1