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Twistor Memory
Twistor memory is a form of computer memory formed by wrapping magnetic tape around a current-carrying wire. Operationally, twistor was very similar to core memory. Twistor could also be used to make ROM memories, including a re-programmable form known as piggyback twistor. Both forms were able to be manufactured using automated processes, which was expected to lead to much lower production costs than core-based systems. Introduced by Bell Labs in 1957, the first commercial use was in their 1ESS switch which went into operation in 1965. Twistor was used only briefly in the late 1960s and early 1970s, when semiconductor memory devices replaced almost all earlier memory systems. The basic ideas behind twistor also led to the development of bubble memory, although this had a similarly short commercial lifespan. Core memory Construction In core memory, small ring-shaped magnets - the cores - are threaded by two crossed wires, ''X'' and ''Y'', to make a matrix known as a ''pla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Memory
Computer memory stores information, such as data and programs, for immediate use in the computer. The term ''memory'' is often synonymous with the terms ''RAM,'' ''main memory,'' or ''primary storage.'' Archaic synonyms for main memory include ''core'' (for magnetic core memory) and ''store''. Main memory operates at a high speed compared to mass storage which is slower but less expensive per bit and higher in capacity. Besides storing opened programs and data being actively processed, computer memory serves as a Page cache, mass storage cache and write buffer to improve both reading and writing performance. Operating systems borrow RAM capacity for caching so long as it is not needed by running software. If needed, contents of the computer memory can be transferred to storage; a common way of doing this is through a memory management technique called ''virtual memory''. Modern computer memory is implemented as semiconductor memory, where data is stored within memory cell (com ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Permalloy
Permalloy () is a nickel–iron magnetic alloy, with about 80% nickel and 20% iron content. Invented in 1914 by physicist Gustav Elmen at Bell Telephone Laboratories, it is notable for its very high magnetic permeability, which makes it useful as a magnetic core material in electrical and electronic equipment, and also in magnetic shielding to block magnetic fields. Commercial permalloy alloys typically have relative permeability of around 100,000, compared to several thousand for ordinary steel. In addition to high permeability, its other magnetic properties are low coercivity, near zero magnetostriction, and significant anisotropic magnetoresistance. The low magnetostriction is critical for industrial applications, allowing it to be used in thin films where variable stresses would otherwise cause a ruinously large variation in magnetic properties. Permalloy's electrical resistivity can vary as much as 5% depending on the strength and the direction of an applied magnetic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Communications In Mexico
Mass media in Mexico are regulated by the Secretariat of Communication and Transportation (''Secretaría de Comunicaciones y Transportes or SCT''), a federal executive cabinet ministry and by the Federal Telecommunications Institute (''Instituto Federal de Telecomunicaciones or IFT''). Mexico's communication services market is among the largest in Latin America, liberalized in the 1990s, with the landmark privatization of Teléfonos de México (Telmex), a previously state-owned monopoly. Since then, new operators have entered the market, but Telmex remains the dominant player. Regulation Founded on 13 May 1891, as the Secretariat of Communications and Public Works, the SCT is divided into three subsecretariats: the Subsecretariat of Infrastructure, the Subsecretariat of Communications and the Subsecretariat of Transportation. The SCT has ceded many of its regulatory functions to the Federal Telecommunications Institute. Radio and television Usage of radio, television an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telephone Switchboard
A telephone switchboard is a device used to connect circuits of telephones to establish telephone calls between users or other switchboards. The switchboard is an essential component of a manual telephone exchange, and is operated by switchboard operators who use electrical cords or switches to establish the connections. The switchboard saw the peak of its use in the 20th century before wider adoption of the electromechanical automatic telephone exchange. The automatic exchange, invented by Almon Strowger in 1888, has replaced most switchboards in central telephone exchanges around the world. Nevertheless, many manual branch exchanges remained operational into the second half of the 20th century in many enterprises. Some establishments, such as the White House, still operate a switchboard. Electronic devices and computer technology have given exchange operators more features. For example, a private branch exchange (PBX) in a business usually has an attendant console, or an auto- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Traffic Service Position System
The Traffic Service Position System (TSPS) was developed by Bell Labs in Columbus, Ohio to replace traditional cord switchboards. The first TSPS was deployed in Morristown, New Jersey in 1969 and used the Stored Program Control-1A CPU, "Piggyback" twistor memory (a proprietary technology developed by Bell Labs similar to core memory) and Insulated Gate Field Effect Transistor solid state memory devices similar to dynamic random access memory. Features The TSPS system utilized special analog trunks that originated at Class 5 end office circuit switch systems and Class 4 toll access circuit switch systems that were connected to Class 3 primary toll circuit switch systems such as the 4A-ETS/PBC and 4ESS switch systems. The TSPS system did not perform switching between the originating end office switch and the toll switch for the subscriber voice path. The TSPS system included the "Remote Trunking Arrangement" (RTA) feature that consolidated the trunk connection at the origina ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
4ESS Switch
The No. 4 Electronic Switching System (4ESS) is a class 4 telephone electronic switching system that was the first digital electronic toll switch introduced by Western Electric for long-distance switching. It was introduced in Chicago in January 1976, to replace the 4A crossbar switch. The last of the 145 systems in the AT&T network was installed in 1999 in Atlanta. Approximately half of the switches were manufactured in Lisle, Illinois, and the other half in Oklahoma City, Oklahoma. At the time of the Bell System divestiture, most of the 4ESS switches became assets of AT&T as part of the long-distance network, while others remained in the RBOC networks. Over 140 4ESS switches remained in service in the United States in 2007. System architecture The 4ESS Switch is often considered as a switching network and its controlling processor. The major functional equipment areas include: * 1B processor, the 4ESS primary controlling processor * 3B computer and associated attached processor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telephone Switch
A telephone exchange, telephone switch, or central office is a central component of a telecommunications system in the public switched telephone network (PSTN) or in large enterprises. It facilitates the establishment of communication circuits, enabling telephone calls between subscribers. The term "central office" can also refer to a central location for fiber optic equipment for a fiber internet provider. In historical perspective, telecommunication terminology has evolved with time. The term ''telephone exchange'' is often used synonymously with ''central office'', a Bell System term. A central office is defined as the telephone switch controlling connections for one or more central office prefixes. However, it also often denotes the building used to house the inside plant equipment for multiple telephone exchange areas. In North America, the term ''wire center'' may be used to denote a central office location, indicating a facility that provides a telephone with a dial tone ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electronic Switching System
In telecommunications, an electronic switching system (ESS) is a telephone switch that uses solid-state electronics, such as digital electronics and computerized common control, to interconnect telephone circuits for the purpose of establishing telephone calls. The generations of telephone switches before the advent of electronic switching in the 1950s used purely electro-mechanical relay systems and analog voice paths. These early machines typically utilized the step-by-step technique. The first generation of electronic switching systems in the 1960s were not entirely digital in nature, but used reed relay-operated metallic paths or crossbar switches operated by stored program control (SPC) systems. First announced in 1955, the first customer trial installation of an all-electronic central office commenced in Morris, Illinois in November 1960 by Bell Laboratories. The first large-scale electronic switching system was the Number One Electronic Switching System (1ESS) of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
American Telephone & Telegraph
AT&T Corporation, an abbreviation for its former name, the American Telephone and Telegraph Company, was an American telecommunications company that provided voice, video, data, and Internet telecommunications and professional services to businesses, consumers, and government agencies. During the Bell System's long history, AT&T was at times the world's largest telecommunications company, the world's largest cable television operator, and a regulated monopoly. At its peak in the 1950s and 1960s, it employed one million people and its revenue ranged between US$3 billion in 1950 ($ in present-day terms) and $12 billion in 1966 ($ in present-day terms). In 2005, AT&T was acquired by "Regional Bell Operating Company, Baby Bell" and former subsidiary SBC Communications for more than $16 billion ($ in present-day terms). SBC then changed its name to AT&T, AT&T Inc., with AT&T Corporation continuing to exist as a long-distance calling subsidiary until its dissolution o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bell System
The Bell System was a system of telecommunication companies, led by the Bell Telephone Company and later by the AT&T Corporation, American Telephone and Telegraph Company (AT&T), that dominated the telephone services industry in North America for over 100 years from its creation in 1877 until United States v. AT&T (1982), its antitrust breakup in 1983. The system of companies was often colloquially called Ma Bell (as in "Mother Bell"), as it held a vertical monopoly over telecommunication products and services in most areas of the United States and Canada. At the time of the breakup of the Bell System in the early 1980s, it had assets of $150 billion (equivalent to $ billion in ) and employed over one million people. Beginning in the 1910s, American antitrust regulators had been observing and accusing the Bell System of abusing its monopoly power, and had brought legal action multiple times over the decades. In 1974 the United States Department of Justice Antitrust Division, Anti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
LIM-49 Nike Zeus
Nike Zeus was an anti-ballistic missile (ABM) system developed by the United States Army during the late 1950s and early 1960s that was designed to destroy incoming Soviet intercontinental ballistic missile warheads before they could hit their targets. It was designed by Bell Labs' Nike team, and was initially based on the earlier Nike Hercules anti-aircraft missile. The original, Zeus A, was designed to intercept warheads in the upper atmosphere, mounting a 25 kiloton W31 nuclear warhead. During development, the concept changed to protect a much larger area and intercept the warheads at higher altitudes. This required the missile to be greatly enlarged into the totally new design, Zeus B, given the tri-service identifier XLIM-49, mounting a 400 kiloton W50 warhead. In several successful tests, the B model proved itself able to intercept warheads, and even satellites. The nature of the strategic threat changed dramatically during the period that Zeus was being developed. Ori ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
US Air Force
The United States Air Force (USAF) is the Air force, air service branch of the United States Department of Defense. It is one of the six United States Armed Forces and one of the eight uniformed services of the United States. Tracing its origins to 1 August 1907, as a part of the United States Army Signal Corps, the USAF was established by transfer of personnel from the Army Air Forces with the enactment of the National Security Act of 1947. It is the second youngest branch of the United States Armed Forces and the fourth in United States order of precedence, order of precedence. The United States Air Force articulates its core missions as air supremacy, intelligence, surveillance, target acquisition, and reconnaissance, global integrated intelligence, surveillance and reconnaissance, airlift, rapid global mobility, Strategic bombing, global strike, and command and control. The United States Department of the Air Force, Department of the Air Force, which serves as the USAF's ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
