Telecommunication
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
Telephone magneto
A telephone magneto is a hand-cranked electrical generator that uses permanent magnets to produce alternating current from the rotating armature. In early telegraphy, magnetos were used to power instruments, while in telephony they were used to generate electrical current to drive electromechanical ringers in telephone sets and on operator consoles. Telegraphy pre-dated telephony and magnetos were used to drive some of the early printing telegraph instruments. Manual telegraphy with keys and reception by either a needle instrument or a syphon recorder could be powered by batteries; the automatic and printing instruments, such as the Wheatstone ABC telegraph, required greater currents that could be delivered by a hand-cranked magneto. A hand-crank was used to rotate a belt drive that increases the rotational speed of an armature with a pair of coils between the poles of a stationary horseshoe magnet. Many early manual telephones had an attached hand-cranked magneto that produced an alternating current at 50-100V for signaling to ring the bells of other telephones on the same line and to alert an operator at the local telephone exchange.
These were most common on long rural lines served by small manual exchanges which did not use a common battery circuit. The telephone instrument contained a local battery, consisting of two large "N° 6" zinc-carbon dry cells, to provide the necessary current for the transmitter. By around 1900, large racks of motor-generator sets in the telephone exchange could supply this ringing current remotely instead and the local magneto was no longer required, but their use continued into the mid-20th century. Telephone magnetos featured a large gear rotated by hand with a handle, that drove a much smaller gear on the armature rotor, providing a high gear-ratio to increase the rotational speed of the magneto armature. A mechanical switch on the output terminals engaged only when the rotor was turning, so that the magneto was disconnected from the telephone circuitry. Ringing current magnetos were used in the public switched telephone network as late as the 1980s, when they were still used with private manual branch exchanges, small business switchboards worked by operators.
Rather than have a motor generator set for such a small installation, which generated noise and required maintenance, these systems used a hand magneto. Unlike on the public telephone network, which has a standard ringing cadence, the ringing cadence on a PMBX depended upon the skill of the operator; when ringing local extensions, some switchboard operators used local codes of ringing to indicate internal, external or urgent calls. Linesman's test sets included a magneto, for use when ringing out to either the exchange or the subscriber, from anywhere along the line, their use extended into the 1980s. Magneto Ringer box
Telephone
A telephone, or phone, is a telecommunications device that permits two or more users to conduct a conversation when they are too far apart to be heard directly. A telephone converts sound and most efficiently the human voice, into electronic signals that are transmitted via cables and other communication channels to another telephone which reproduces the sound to the receiving user. In 1876, Scottish emigrant Alexander Graham Bell was the first to be granted a United States patent for a device that produced intelligible replication of the human voice; this instrument was further developed by many others. The telephone was the first device in history that enabled people to talk directly with each other across large distances. Telephones became indispensable to businesses and households and are today some of the most used small appliances; the essential elements of a telephone are a microphone to speak into and an earphone which reproduces the voice in a distant location. In addition, most telephones contain a ringer to announce an incoming telephone call, a dial or keypad to enter a telephone number when initiating a call to another telephone.
The receiver and transmitter are built into a handset, held up to the ear and mouth during conversation. The dial may be located either on a base unit to which the handset is connected; the transmitter converts the sound waves to electrical signals which are sent through a telephone network to the receiving telephone, which converts the signals into audible sound in the receiver or sometimes a loudspeaker. Telephones are duplex devices; the first telephones were directly connected to each other from one customer's office or residence to another customer's location. Being impractical beyond just a few customers, these systems were replaced by manually operated centrally located switchboards; these exchanges were soon connected together forming an automated, worldwide public switched telephone network. For greater mobility, various radio systems were developed for transmission between mobile stations on ships and automobiles in the mid-20th century. Hand-held mobile phones were introduced for personal service starting in 1973.
In decades their analog cellular system evolved into digital networks with greater capability and lower cost. Convergence has given most modern cell phones capabilities far beyond simple voice conversation, they may be able to record spoken messages and receive text messages and display photographs or video, play music or games, surf the Internet, do road navigation or immerse the user in virtual reality. Since 1999, the trend for mobile phones is smartphones that integrate all mobile communication and computing needs. A traditional landline telephone system known as plain old telephone service carries both control and audio signals on the same twisted pair of insulated wires, the telephone line; the control and signaling equipment consists of three components, the ringer, the hookswitch, a dial. The ringer, or beeper, light or other device, alerts the user to incoming calls; the hookswitch signals to the central office that the user has picked up the handset to either answer a call or initiate a call.
A dial, if present, is used by the subscriber to transmit a telephone number to the central office when initiating a call. Until the 1960s dials used exclusively the rotary technology, replaced by dual-tone multi-frequency signaling with pushbutton telephones. A major expense of wire-line telephone service is the outside wire plant. Telephones transmit both the outgoing speech signals on a single pair of wires. A twisted pair line rejects electromagnetic interference and crosstalk better than a single wire or an untwisted pair; the strong outgoing speech signal from the microphone does not overpower the weaker incoming speaker signal with sidetone because a hybrid coil and other components compensate the imbalance. The junction box arrests lightning and adjusts the line's resistance to maximize the signal power for the line length. Telephones have similar adjustments for inside line lengths; the line voltages are negative compared to earth. Negative voltage attracts positive metal ions toward the wires.
The landline telephone contains a switchhook and an alerting device a ringer, that remains connected to the phone line whenever the phone is "on hook", other components which are connected when the phone is "off hook". The off-hook components include a transmitter, a receiver, other circuits for dialing and amplification. A calling party wishing to speak to another party will pick up the telephone's handset, thereby operating a lever which closes the switchhook, which powers the telephone by connecting the transmitter and related audio components to the line; the off-hook circuitry has a low resistance which causes a direct current, which comes down the line from the telephone exchange. The exchange detects this current, attaches a digit receiver circuit to the line, sends a dial tone to indicate readiness. On a modern push-button telephone, the caller presses the number keys to send the telephone number of the called party; the keys control a tone generator circuit. A rotary-dial telephone uses pulse
Intercom
An intercom, talkback or doorphone is a stand-alone voice communications system for use within a building or small collection of buildings, functioning independently of the public telephone network. Intercoms are mounted permanently in buildings and vehicles. Intercoms can incorporate connections to public address loudspeaker systems, walkie talkies, to other intercom systems; some intercom systems incorporate control of devices such as signal lights and door latches. There are simple house intercoms developed for collective apartments; some are equipped with video, its wiring, can be connected to the outside with few pairs while controlling an electric strike. The last generations are compatible with computers and some models include TCP/IP. Traditional intercoms and public address systems are composed of analogue electronics components but many new features and interfacing options can be accomplished with new intercom systems based on digital connections. Video signals can be carried as well as voice.
Digital intercom stations can be connected using Cat 5 cable and can use existing computer networks as a means of interfacing distant parties. Many schools and office buildings now use audio / video systems to identify visitors trying to gain access to a locked building, can be interfaced with the building's access control system. Besides fixed locations, intercom systems are used on many types of vehicles including trains, watercraft and armoured fighting vehicles. Portable intercoms are used by special event production crews and professional sports teams. Performing arts venues such as theaters and concert halls have a combination of permanently mounted and portable intercom elements. Motorsports race tracks have both portable and permanent intercom stations mounted at critical points around the racecourse for use by race officials and emergency medical technicians. Master Station or Base Station – These are units that can control the system, i.e. initiate a call with any of the stations and make announcements over the whole system.
Sub-station - Units that are capable of only initiating a call with a Master Station but not capable of initiating calls with any other stations. Door Station - Like sub-stations, these units are only capable of initiating a call to a Master Station, they are weather-proof. Intercom Station - Full-featured remote unit, capable of initiating and receiving party-line conversation, individual conversation and signalling. May be wall-mounted or portable. Wall Mount Station – fixed-position intercom station with built-in loudspeaker. May have flush-mounted microphone, hand-held push to talk telephone-style handset. Belt Pack - portable intercom station worn on the belt such as an interruptible feedback with an earpiece worn by talent. Handset - permanent or portable telephone-style connection to an intercom station. Holds both an earpiece and a push to talk microphone. Headset - portable intercom connection from a belt pack to one or both ears via headphones with integrated microphone on a boom arm. Connects to a belt pack.
Paging Signal - An audible and/or visual alert at an intercom station, indicating that someone at another station wants to initiate a conversation. Power Supply - Used to feed power to all units. Incorporated into the design of the base station. Telephonic - Intercom systems that utilize a transmitter and receiver to communicate, similar to standard telephone systems. Amplified - Intercom systems that utilize a single speaker to transmit and receive communications. Amplifier - An intercom systems main or central component, responsible for switching or connecting communication paths between master and substations in addition to distributing or switching power to auxiliary connected devices i.e. door strikes to allow entry. While every intercom product line is different, most analogue intercom systems have much in common. Voice signals of about a volt or two are carried atop a direct current power rail of 12, 30 or 48 volts which uses a pair of conductors. Signal light indications between stations can be accomplished through the use of additional conductors or can be carried on the main voice pair via tone frequencies sent above or below the speech frequency range.
Multiple channels of simultaneous conversations can be carried over additional conductors within a cable or by frequency- or time-division multiplexing in the analogue domain. Multiple channels can be carried by packet-switched digital intercom signals. Portable intercoms are connected using common shielded, twisted pair microphone cabling terminated with 3-pin XLR connectors. Building and vehicle intercoms are connected in a similar manner with shielded cabling containing more than one twisted pair. Digital intercoms use Category 5 cable and relay information back and forth in data packets using the Internet protocol architecture. Intercom systems are used in TV stations and outside broadcast vehicles such as those seen at sporting events or entertainment venues. There are two different types of intercoms used in the television world: two-wire party line or four-wire matrix systems. In the beginning, TV stations would build their own communication systems using old phone equipment. However, today there are several manufacturers offering off-the-shelf systems.
From the late 1970s until the mid-90s, the two-wire party line-type systems were the most popular due to the technology, available at the time. The two-channel variety used a 32-volt impedance-generating central power supply to drive external stations or belt packs; this type
Party line (telephony)
A party line is a local loop telephone circuit, shared by multiple telephone service subscribers. Party line systems were used to provide telephone service, starting with the first commercial switchboards in 1878. A majority of Bell System subscribers in the mid-20th century in the United States and Canada were serviced by party lines, which carried a billing discount over individual service. British users benefited from the party line discount. Farmers in rural Australia used party lines, where a single line spanned miles from the nearest town to one property and on to the next. Telephone companies offered party lines since the late 1800s, although subscribers in all but the most rural areas may have had the option to upgrade to individual line service at an additional monthly charge; the service was common in sparsely populated areas where remote properties were spread across large distances. An example is Australia. In rural areas in the early 20th century, additional subscribers and telephones numbering several dozen, were connected to the single loop available.
Party lines provided no privacy in communication. They were used as a source of entertainment and gossip, as well as a means of alerting entire neighbourhoods of emergencies such as fires, becoming a cultural fixture of rural areas for many decades; the rapid growth of telephone service demand after World War II, resulted in a large fraction of party line installations in the middle of the 20th century in the United States. This led to traffic congestion in the telephone network, as the line to a destination telephone was busy. Nearly three-quarters of Pennsylvania residential service in 1943 was party line, with users encouraged to limit calls to five minutes. Shortages persisted for years after each war; some rural users had to run their own wires to reach the utility's lines. Objections about one party monopolizing a multi-party line were a staple of complaints to telephone companies and letters to advice columnists for years and eavesdropping on calls remained an ongoing concern. In December 1942, University of Tennessee's strategy in an American football game versus University of Mississippi was revealed to the opposing coach as a telephone on the Ole Miss team's bench had been inadvertently wired to the same party line.
In May 1952, an alleged bookmaking operation in St. Petersburg, Florida was shut down after one month of operation in a rented storefront using a party-line telephone. In June 1968, the conviction of three Winter Park, Florida men on bookmaking charges was overturned as police had used a party-line telephone in a rented house on the same line as the suspects to unlawfully intercept their communications. In 1956, Southern Bell officials refused a request from a public utilities commissioner in Jackson, Mississippi to segregate party telephone lines on racial boundaries. While primitive lockout devices to prevent two subscribers from picking up the same line at the same time were proposed early, multiple simultaneous calls did not become viable until the initial tests of transistorised pair gain devices in 1955. Any handset off-hook therefore tied up the line for everyone. Many jurisdictions require a person engaged in a call on a party line to end the call if another party needs the line for an emergency.
Such laws provide penalties for abuse by falsifying emergency situations. In May 1955, a Rhinebeck, New York woman was indicted by a grand jury after her refusal to relinquish a party line delayed a volunteer firefighter's effort to report a grass fire, she was given a suspended sentence. In June 1970, a sixteen-year-old girl and a woman were charged after refusing to relinquish a party line to allow a distress call as three boys drowned in a pond in Walsenburg, Colorado. By the 1980s, party lines were removed in most localities, they could not support new technologies and subscriber-owned equipment such as answering machines and computer modems. Meanwhile, the electro-mechanical switching equipment required for their operation was becoming obsolete, supplanted by electronic and digital switching equipment; the new telephone exchange equipment offered vertical service code calling features such as call forwarding and call waiting, but was incompatible with multi-party lines. Party lines in the United States were ineligible for Universal Service Fund subsidies, leading telephone companies to convert them to individual lines to benefit from these subsidies.
In 1971, Southern Bell announced plans to phase out all party lines in North Carolina. One of the last manual telephone exchanges with party lines in Australia was closed down in 1986 in the township of Collarenebri, where most town residents had a telephone number of only three digits, to make a call outside the exchange area it was necessary to call the exchange to place a call. For rural residents, many were on a single telephone line identified by a number and a property name, such as "Gundabluie 1"; each party on that single line was identified by a letter, the ringing pattern for that party would consist of the corresponding letter in Morse code. This distinctive ring would alert all parties on the line. In 1989, the Chesapeake and Potomac Telephone Company replaced party lines with individual lines in Talcott, West Virginia, a rural area which once had as many as sixteen subscribers on one line
Computer network
A computer network is a digital telecommunications network which allows nodes to share resources. In computer networks, computing devices exchange data with each other using connections between nodes; these data links are established over cable media such as wires or optic cables, or wireless media such as Wi-Fi. Network computer devices that originate and terminate the data are called network nodes. Nodes are identified by network addresses, can include hosts such as personal computers and servers, as well as networking hardware such as routers and switches. Two such devices can be said to be networked together when one device is able to exchange information with the other device, whether or not they have a direct connection to each other. In most cases, application-specific communications protocols are layered over other more general communications protocols; this formidable collection of information technology requires skilled network management to keep it all running reliably. Computer networks support an enormous number of applications and services such as access to the World Wide Web, digital video, digital audio, shared use of application and storage servers and fax machines, use of email and instant messaging applications as well as many others.
Computer networks differ in the transmission medium used to carry their signals, communications protocols to organize network traffic, the network's size, traffic control mechanism and organizational intent. The best-known computer network is the Internet; the chronology of significant computer-network developments includes: In the late 1950s, early networks of computers included the U. S. military radar system Semi-Automatic Ground Environment. In 1959, Anatolii Ivanovich Kitov proposed to the Central Committee of the Communist Party of the Soviet Union a detailed plan for the re-organisation of the control of the Soviet armed forces and of the Soviet economy on the basis of a network of computing centres, the OGAS. In 1960, the commercial airline reservation system semi-automatic business research environment went online with two connected mainframes. In 1963, J. C. R. Licklider sent a memorandum to office colleagues discussing the concept of the "Intergalactic Computer Network", a computer network intended to allow general communications among computer users.
In 1964, researchers at Dartmouth College developed the Dartmouth Time Sharing System for distributed users of large computer systems. The same year, at Massachusetts Institute of Technology, a research group supported by General Electric and Bell Labs used a computer to route and manage telephone connections. Throughout the 1960s, Paul Baran and Donald Davies independently developed the concept of packet switching to transfer information between computers over a network. Davies pioneered the implementation of the concept with the NPL network, a local area network at the National Physical Laboratory using a line speed of 768 kbit/s. In 1965, Western Electric introduced the first used telephone switch that implemented true computer control. In 1966, Thomas Marill and Lawrence G. Roberts published a paper on an experimental wide area network for computer time sharing. In 1969, the first four nodes of the ARPANET were connected using 50 kbit/s circuits between the University of California at Los Angeles, the Stanford Research Institute, the University of California at Santa Barbara, the University of Utah.
Leonard Kleinrock carried out theoretical work to model the performance of packet-switched networks, which underpinned the development of the ARPANET. His theoretical work on hierarchical routing in the late 1970s with student Farouk Kamoun remains critical to the operation of the Internet today. In 1972, commercial services using X.25 were deployed, used as an underlying infrastructure for expanding TCP/IP networks. In 1973, the French CYCLADES network was the first to make the hosts responsible for the reliable delivery of data, rather than this being a centralized service of the network itself. In 1973, Robert Metcalfe wrote a formal memo at Xerox PARC describing Ethernet, a networking system, based on the Aloha network, developed in the 1960s by Norman Abramson and colleagues at the University of Hawaii. In July 1976, Robert Metcalfe and David Boggs published their paper "Ethernet: Distributed Packet Switching for Local Computer Networks" and collaborated on several patents received in 1977 and 1978.
In 1979, Robert Metcalfe pursued making Ethernet an open standard. In 1976, John Murphy of Datapoint Corporation created ARCNET, a token-passing network first used to share storage devices. In 1995, the transmission speed capacity for Ethernet increased from 10 Mbit/s to 100 Mbit/s. By 1998, Ethernet supported transmission speeds of a Gigabit. Subsequently, higher speeds of up to 400 Gbit/s were added; the ability of Ethernet to scale is a contributing factor to its continued use. Computer networking may be considered a branch of electrical engineering, electronics engineering, telecommunications, computer science, information technology or computer engineering, since it relies upon the theoretical and practical application of the related disciplines. A computer network facilitates interpersonal communications allowing users to communicate efficiently and via various means: email, instant messaging, online chat, video telephone calls, video conferencing. A network allows sharing of computing resources.
Users may access and use resources provided by devices on the network, such as printing a document on a shared network printer or use of a shared storage device. A network allows sharing of files, and
Cisco Systems
Cisco Systems, Inc. is an American multinational technology conglomerate headquartered in San Jose, California, in the center of Silicon Valley. Cisco develops and sells networking hardware, telecommunications equipment and other high-technology services and products. Through its numerous acquired subsidiaries, such as OpenDNS, WebEx, Jabber and Jasper, Cisco specializes into specific tech markets, such as Internet of Things, domain security and energy management. Cisco stock was added to the Dow Jones Industrial Average on June 8, 2009, is included in the S&P 500 Index, the Russell 1000 Index, NASDAQ-100 Index and the Russell 1000 Growth Stock Index. Cisco Systems was founded in December 1984 by Leonard Bosack and Sandy Lerner, two Stanford University computer scientists, they pioneered the concept of a local area network being used to connect geographically disparate computers over a multiprotocol router system. By the time the company went public in 1990, Cisco had a market capitalization of $224 million.
By the end of the dot-com bubble in the year 2000, Cisco had a more than $500 billion market capitalization. Cisco Systems was founded in December 1984 by Sandy Lerner, a director of computer facilities for the Stanford University Graduate School of Business. Lerner partnered with her husband, Leonard Bosack, in charge of the Stanford University computer science department's computers. Cisco's initial product has roots in Stanford University's campus technology. In the early 1980's students and staff at Stanford; the Blue Box used software, written at Stanford by research engineer William Yeager. In 1985, Bosack and Stanford employee Kirk Lougheed began a project to formally network Stanford's campus, they adapted Yeager's software into what became the foundation for Cisco IOS, despite Yeager's claims that he had been denied permission to sell the Blue Box commercially. On July 11, 1986, Bosack and Lougheed were forced to resign from Stanford and the university contemplated filing criminal complaints against Cisco and its founders for the theft of its software, hardware designs, other intellectual properties.
In 1987, Stanford licensed two computer boards to Cisco. In addition to Bosack, Lougheed, Greg Satz, Richard Troiano, completed the early Cisco team; the company's first CEO was Bill Graves, who held the position from 1987 to 1988. In 1988, John Morgridge was appointed CEO; the name "Cisco" was derived from the city name San Francisco, why the company's engineers insisted on using the lower case "cisco" in its early years. The logo is intended to depict the two towers of the Golden Gate Bridge. On February 16, 1990, Cisco Systems went public with a market capitalization of $224 million, was listed on the NASDAQ stock exchange. On August 28, 1990, Lerner was fired. Upon hearing the news, her husband Bosack resigned in protest; the couple walked away from Cisco with $170 million, 70% of, committed to their own charity. Although Cisco was not the first company to develop and sell dedicated network nodes, it was one of the first to sell commercially successful routers supporting multiple network protocols.
Classical, CPU-based architecture of early Cisco devices coupled with flexibility of operating system IOS allowed for keeping up with evolving technology needs by means of frequent software upgrades. Some popular models of that time managed to stay in production for a decade unchanged; the company was quick to capture the emerging service provider environment, entering the SP market with product lines such as Cisco 7000 and Cisco 8500. Between 1992 and 1994, Cisco acquired several companies in Ethernet switching, such as Kalpana, Grand Junction and most notably, Mario Mazzola's Crescendo Communications, which together formed the Catalyst business unit. At the time, the company envisioned layer 3 routing and layer 2 switching as complementary functions of different intelligence and architecture—the former was slow and complex, the latter was fast but simple; this philosophy dominated the company's product lines throughout the 1990s. In 1995, John Morgridge was succeeded by John Chambers; the Internet Protocol became adopted in the mid-to-late 1990s.
Cisco introduced products ranging from modem access shelves to core GSR routers, making them a major player in the market. In late March 2000, at the height of the dot-com bubble, Cisco became the most valuable company in the world, with a market capitalization of more than $500 billion; as of July 2014, with a market cap of about US$129 billion, it was still one of the most valuable companies. The perceived complexity of programming routing functions in silicon led to the formation of several startups determined to find new ways to process IP and MPLS packets in hardware and blur boundaries between routing and switching. One of them, Juniper Networks, shipped their first product in 1999 and by 2000 chipped away about 30% from Cisco SP Market share. In response, Cisco developed homegrown ASICs and fast processing cards for GSR routers and Catalyst 6500 switches. In 2004, Cisco started migration to new high-end hardware CRS-1 and software architecture IOS-XR; as part of a rebranding campaign in 2006, Cisco Systems adopted the shortened name "Cisco" and created "The Human Network" advertising campaign.
These efforts were meant to make Cisco a "household" brand—a strategy designed to support the low-end Linksys products and future consumer products. On the more traditional business side, Cisco cont
This article incorporates public domain material from the General Services Administration document "Federal Standard 1037C" (in support of MIL-STD-188).
This article incorporates 
