1.
BBC
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The British Broadcasting Corporation is a British public service broadcaster. It is headquartered at Broadcasting House in London, the BBC is the worlds oldest national broadcasting organisation and the largest broadcaster in the world by number of employees. It employs over 20,950 staff in total,16,672 of whom are in public sector broadcasting, the total number of staff is 35,402 when part-time, flexible, and fixed contract staff are included. The BBC is established under a Royal Charter and operates under its Agreement with the Secretary of State for Culture, Media and Sport. The fee is set by the British Government, agreed by Parliament, and used to fund the BBCs radio, TV, britains first live public broadcast from the Marconi factory in Chelmsford took place in June 1920. It was sponsored by the Daily Mails Lord Northcliffe and featured the famous Australian Soprano Dame Nellie Melba, the Melba broadcast caught the peoples imagination and marked a turning point in the British publics attitude to radio. However, this public enthusiasm was not shared in official circles where such broadcasts were held to interfere with important military and civil communications. By late 1920, pressure from these quarters and uneasiness among the staff of the licensing authority, the General Post Office, was sufficient to lead to a ban on further Chelmsford broadcasts. But by 1922, the GPO had received nearly 100 broadcast licence requests, John Reith, a Scottish Calvinist, was appointed its General Manager in December 1922 a few weeks after the company made its first official broadcast. The company was to be financed by a royalty on the sale of BBC wireless receiving sets from approved manufacturers, to this day, the BBC aims to follow the Reithian directive to inform, educate and entertain. The financial arrangements soon proved inadequate, set sales were disappointing as amateurs made their own receivers and listeners bought rival unlicensed sets. By mid-1923, discussions between the GPO and the BBC had become deadlocked and the Postmaster-General commissioned a review of broadcasting by the Sykes Committee and this was to be followed by a simple 10 shillings licence fee with no royalty once the wireless manufactures protection expired. The BBCs broadcasting monopoly was made explicit for the duration of its current broadcast licence, the BBC was also banned from presenting news bulletins before 19.00, and required to source all news from external wire services. Mid-1925 found the future of broadcasting under further consideration, this time by the Crawford committee, by now the BBC under Reiths leadership had forged a consensus favouring a continuation of the unified broadcasting service, but more money was still required to finance rapid expansion. Wireless manufacturers were anxious to exit the loss making consortium with Reith keen that the BBC be seen as a service rather than a commercial enterprise. The recommendations of the Crawford Committee were published in March the following year and were still under consideration by the GPO when the 1926 general strike broke out in May. The strike temporarily interrupted newspaper production and with restrictions on news bulletins waived the BBC suddenly became the source of news for the duration of the crisis. The crisis placed the BBC in a delicate position, the Government was divided on how to handle the BBC but ended up trusting Reith, whose opposition to the strike mirrored the PMs own
2.
Digital video recorder
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A digital video recorder is an electronic device that records video in a digital format to a disk drive, USB flash drive, SD memory card, SSD or other local or networked mass storage device. The term includes set-top boxes with direct to disk recording, portable media players and TV gateways with recording capability, and digital camcorders. Personal computers are connected to video capture devices and used as DVRs. Many DVRs are classified as electronic devices, such devices are sometimes referred to as personal video recorders. Consumer digital video recorders ReplayTV and TiVo were launched at the 1999 Consumer Electronics Show in Las Vegas, Microsoft also demonstrated a unit with DVR capability, but this did not become available until the end of 1999 for full DVR features in Dish Networks DISHplayer receivers. TiVo shipped their first units on March 31,1999, ReplayTV won the Best of Show award in the video category with Netscape co-founder Marc Andreessen as an early investor and board member, but TiVo was more successful commercially. Many DVRs use the MPEG format for compressing the digital video, video recording capabilities have become an essential part of the modern set-top box, as TV viewers have wanted to take control of their viewing experiences. Digital video recorders tied to a video service At the 1999 CES, which also included WebTV Networks internet TV. By the end of 1999 the Dishplayer had full DVR capabilities and within a year, in the UK, digital video recorders are often referred to as plus boxes. Freeview+ have been around in the UK since the late 2000s, british Sky Broadcasting markets a popular combined receiver and DVR as Sky+. TiVo launched a UK model in 2000, and is no longer supported, except for third party services, south African based Africa Satellite TV beamer Multichoice recently launched their DVR which is available on their DStv platform. Astro introduced their DVR system, called Astro MAX, which was the first PVR in Malaysia but was phased out two years after its introduction. In the case of television, there is no encoding necessary in the DVR since the signal is already a digitally encoded MPEG stream. The digital video recorder simply stores the digital stream directly to disk and it can, however, also force the manufacturer to implement non-skippable advertisements and automatically expiring recordings. The overall net effect on video recorders and related technology is unlikely to be substantial as standalone DVRs are currently readily available on the open market. In 2003 many Satellite and Cable providers introduced dual-tuner digital video recorders, in the UK, BSkyB introduced their first PVR Sky+ with dual tuner support in 2001. These machines have two independent tuners within the same receiver, kogan. com introduced a dual-tuner PVR in the Australian market allowing free-to-air television to be recorded on a removable hard drive. Some dual-tuner DVRs also have the ability to output to two television sets at the same time
3.
Television program
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It may be a single production, or more commonly, a series of related productions. A limited number of episodes of a show may be called a miniseries or a serial or limited series. Television series are without a fixed length and are divided into seasons or series. While there is no defined length, U. S. industry practice has traditionally favored longer television seasons than those of other countries, a one-time broadcast may be called a special, or particularly in the UK a special episode. A television film is a film that is initially broadcast on television rather than released in theaters or direct-to-video, a program can be either recorded, as on video tape, other various electronic media forms, played with an on-demand player or viewed on live television. Television programs may be fictional, or non-fictional and it may be topical, or historical. They could be primarily instructional or educational, or entertaining as is the case in situation comedy, a drama program usually features a set of actors playing characters in a historical or contemporary setting. The program follows their lives and adventures, except for soap opera-type serials, many shows especially before the 1980s, remained static without story arcs, and the main characters and premise changed little. If some change happened to the characters lives during the episode, because of this, the episodes could be broadcast in any order. Since the 1980s, there are series that feature progressive change to the plot. For instance, Hill Street Blues and St. Elsewhere were two of the first American prime time television series to have this kind of dramatic structure. While the later series, Babylon 5 is an example of such production that had a predetermined story running over its intended five-season run. In 2012, it was reported that television was growing into a component of major media companies revenues than film. Some also noted the increase in quality of television programs. When a person or company decides to create a new series, they develop the elements, consisting of the concept, the characters, the crew. Then they offer it to the networks in an attempt to find one interested enough to order a prototype first episode of the series. They want very much to get the word out on what types of shows they’re looking for, to create the pilot, the structure and team of the whole series must be put together. If the network likes the pilot, they pick up the show to air it the next season, sometimes they save it for mid-season, or request rewrites and further review
4.
Sun Fire
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Sun Fire is a series of server computers introduced in 2001 by Sun Microsystems. The Sun Fire branding coincided with the introduction of the UltraSPARC III processor, in 2003, Sun broadened the Sun Fire brand, introducing Sun Fire servers using the Intel Xeon processor. In 2004, these early Intel Xeon models were superseded by models powered by AMD Opteron processors, also in 2004, Sun introduced Sun Fire servers powered by the UltraSPARC IV dual-core processor. In 2007, Sun again introduced Intel Xeon Sun Fire servers, sPARC-based Sun Fire systems were produced until 2010, while x86-64 based machines were marketed until mid-2012. In mid-2012, Oracle Corporation ceased to use the Sun Fire brand for new server models, ultraSPARC-based Sun Fire models are licensed to run the Solaris operating system versions 8,9, and 10. Although not officially supported, some Linux versions are available from third parties. The z suffix was used previously to differentiate the V880z Visualization Server variant of the V880 server. Suns first-generation blade server platform, the Sun Fire B1600 chassis, later Sun blade systems were sold under the Sun Blade brand. In 2007, Sun, Fujitsu and Fujitsu Siemens introduced the common SPARC Enterprise brand for server products, the first SPARC Enterprise models were the Fujitsu-developed successors to the midrange and high-end Sun Fire E-series. Later T-series servers have also been badged SPARC Enterprise rather than Sun Fire, some servers were produced in two versions, the original version and a later RoHS version. As of 2012, the x86 server range continued under the Sun Server or Oracle Server names, fireplane Sun System Handbook, Version 2.1
5.
Serial Attached SCSI
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Serial Attached SCSI is a point-to-point serial protocol that moves data to and from computer storage devices such as hard drives and tape drives. SAS replaces the older Parallel SCSI bus technology that first appeared in the mid-1980s, SAS, like its predecessor, uses the standard SCSI command set. SAS offers optional compatibility with SATA, versions 2 and later and this allows for SATA drives to be connected to most SAS backplanes or controllers. The reverse, connecting SAS drives to SATA backplanes, is not possible, the T10 technical committee of the International Committee for Information Technology Standards develops and maintains the SAS protocol, the SCSI Trade Association promotes the technology. Initiators may be provided as a component on the motherboard or as an add-on host bus adapter. A target, a device containing logical units and target ports that receives device service and task management requests for processing, a target device could be a hard disk or a disk array system. A service delivery subsystem, the part of an I/O system that transmits information between an initiator and a target, typically cables connecting an initiator and target with or without expanders and backplanes constitute a service delivery subsystem. Expanders, devices that form part of a delivery subsystem. Expanders facilitate the connection of multiple SAS End devices to a single initiator port, sAS-1,3.0 Gbit/s, introduced in 2004 SAS-2,6.0 Gbit/s, available since February 2009 SAS-3,12.0 Gbit/s, available since March 2013 SAS-4,22. Each SAS port in a SAS domain has a SCSI port identifier that identifies the port uniquely within the SAS domain and it is assigned by the device manufacturer, like an Ethernet devices MAC address, and is typically worldwide unique as well. SAS devices use these port identifiers to address communications to each other, in addition, every SAS device has a SCSI device name, which identifies the SAS device uniquely in the world. One doesnt often see these names because the port identifiers tend to identify the device sufficiently. For comparison, in parallel SCSI, the SCSI ID is the port identifier, in Fibre Channel, the port identifier is a WWPN and the device name is a WWNN. In SAS, both SCSI port identifiers and SCSI device names take the form of a SAS address, which is a 64 bit value, people sometimes refer to a SCSI port identifier as the SAS address of a device, out of confusion. People sometimes call a SAS address a World Wide Name or WWN, for a SAS expander device, the SCSI port identifier and SCSI device name are the same SAS address. The SAS bus operates point-to-point while the SCSI bus is multidrop, each SAS device is connected by a dedicated link to the initiator, unless an expander is used. If one initiator is connected to one target, there is no opportunity for contention, with parallel SCSI, SAS has no termination issues and does not require terminator packs like parallel SCSI. SAS allows up to 65,535 devices through the use of expanders, SAS allows a higher transfer speed than most parallel SCSI standards
6.
Serial ATA
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Serial ATA is a computer bus interface that connects host bus adapters to mass storage devices such as hard disk drives, optical drives, and solid-state drives. Although, a number of hot plug PATA offering were first invented and marketed by Core International beginning in the late 1980s for the Micro Channel architecture bus controllers, prior to SATAs introduction in 2003, the PATA was simply known as ATA. The AT Attachment name originated after the 1984 release of the IBM Personal Computer AT, the IBM AT was the first mass-produced computer where the hard disk was key to the systems performance. The IBM AT’s controller interface became a de facto industry interface for the inclusion of hard disks, SATA host adapters and devices communicate via a high-speed serial cable over two pairs of conductors. In contrast, parallel ATA uses a 16-bit wide data bus with many support and control signals. To ensure backward compatibility with legacy ATA software and applications, SATA uses the same basic ATA, SATA has replaced parallel ATA in consumer desktop and laptop computers, SATAs market share in the desktop PC market was 99% in 2008. A2008 standard, CFast to replace CompactFlash is based on SATA, Serial ATA industry compatibility specifications originate from the Serial ATA International Organization. The SATA-IO group collaboratively creates, reviews, ratifies, and publishes the interoperability specifications, the remainder of this article will try to use the terminology and specifications of SATA-IO. The term Hot Plug was a registered trademark issued by the USPTO and it was invented for computer components including PATA in the late 1980s by Hal Prewitt, founder of Core International. First patent details were disclosed in 1987 in USA and Europe related to development of the technology to connect host bus adapters to mass storage device however the filings were not completed. Core created and in 1990 marketed the worlds first disk controller, host adapter, disk drives, disk arrays, initial implementations were on the IBM PS/2 series and Micro Channel architecture bus controllers. The Serial ATA Spec includes logic for SATA device hotplugging, Devices and motherboards that meet the interoperability specification are capable of hot plugging. Unlike PATA, both SATA and eSATA support hot swapping by design, however, this feature requires proper support at the host, device, and operating-system levels. In general, all SATA devices support hot swapping, also most SATA host adapters support this command, advanced Host Controller Interface is an open host controller interface published and used by Intel, which has become a de facto standard. It allows the use of advanced features of SATA such as hotplug, if AHCI is not enabled by the motherboard and chipset, SATA controllers typically operate in IDE emulation mode, which does not allow access to device features not supported by the ATA standard. Even in those instances, a driver may have been created for a specific chipset. SATA revisions are often designated with a dash followed by roman numerals, e. g. SATA-III, to avoid confusion with the speed, revision 1. 0a was released on January 7,2003. First-generation SATA interfaces, now known as SATA1.5 Gbit/s, communicate at a rate of 1.5 Gbit/s, taking 8b/10b encoding overhead into account, they have an actual uncoded transfer rate of 1.2 Gbit/s
7.
Hard disk drive
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The platters are paired with magnetic heads, usually arranged on a moving actuator arm, which read and write data to the platter surfaces. Data is accessed in a manner, meaning that individual blocks of data can be stored or retrieved in any order. HDDs are a type of storage, retaining stored data even when powered off. Introduced by IBM in 1956, HDDs became the dominant secondary storage device for computers by the early 1960s. Continuously improved, HDDs have maintained this position into the era of servers. More than 200 companies have produced HDDs historically, though after extensive industry consolidation most current units are manufactured by Seagate, Toshiba, as of 2016, HDD production is growing, although unit shipments and sales revenues are declining. While SSDs have higher cost per bit, SSDs are replacing HDDs where speed, power consumption, small size, the primary characteristics of an HDD are its capacity and performance. Capacity is specified in unit prefixes corresponding to powers of 1000, the two most common form factors for modern HDDs are 3. 5-inch, for desktop computers, and 2. 5-inch, primarily for laptops. HDDs are connected to systems by standard interface cables such as PATA, SATA, Hard disk drives were introduced in 1956, as data storage for an IBM real-time transaction processing computer and were developed for use with general-purpose mainframe and minicomputers. The first IBM drive, the 350 RAMAC in 1956, was approximately the size of two medium-sized refrigerators and stored five million six-bit characters on a stack of 50 disks. In 1962 the IBM350 RAMAC disk storage unit was superseded by the IBM1301 disk storage unit, cylinder-mode read/write operations were supported, and the heads flew about 250 micro-inches above the platter surface. Motion of the head array depended upon a binary system of hydraulic actuators which assured repeatable positioning. The 1301 cabinet was about the size of three home refrigerators placed side by side, storing the equivalent of about 21 million eight-bit bytes, access time was about a quarter of a second. Also in 1962, IBM introduced the model 1311 disk drive, users could buy additional packs and interchange them as needed, much like reels of magnetic tape. Later models of removable pack drives, from IBM and others, became the norm in most computer installations, non-removable HDDs were called fixed disk drives. Some high-performance HDDs were manufactured with one head per track so that no time was lost physically moving the heads to a track, known as fixed-head or head-per-track disk drives they were very expensive and are no longer in production. In 1973, IBM introduced a new type of HDD code-named Winchester and its primary distinguishing feature was that the disk heads were not withdrawn completely from the stack of disk platters when the drive was powered down. Instead, the heads were allowed to land on an area of the disk surface upon spin-down
8.
Sun Microsystems
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Sun contributed significantly to the evolution of several key computing technologies, among them Unix, RISC processors, thin client computing, and virtualized computing. Sun was founded on February 24,1982, at its height, the Sun headquarters were in Santa Clara, California, on the former west campus of the Agnews Developmental Center. On January 27,2010, Oracle Corporation acquired Sun by for US$7.4 billion, other technologies include the Java platform, MySQL, and NFS. Sun was a proponent of open systems in general and Unix in particular, the initial design for what became Suns first Unix workstation, the Sun-1, was conceived by Andy Bechtolsheim when he was a graduate student at Stanford University in Palo Alto, California. Bechtolsheim originally designed the SUN workstation for the Stanford University Network communications project as a personal CAD workstation and it was designed around the Motorola 68000 processor with an advanced memory management unit to support the Unix operating system with virtual memory support. He built the first ones from spare parts obtained from Stanfords Department of Computer Science, on February 24,1982, Vinod Khosla, Andy Bechtolsheim, and Scott McNealy, all Stanford graduate students, founded Sun Microsystems. Bill Joy of Berkeley, a developer of the Berkeley Software Distribution. The Sun name is derived from the initials of the Stanford University Network, Sun was profitable from its first quarter in July 1982. By 1983 Sun was known for producing 68000-based systems with high-quality graphics that were the only computers other than DECs VAX to run 4. 2BSD and it licensed the computer design to other manufacturers, which typically used it to build Multibus-based systems running Unix from UniSoft. Suns initial public offering was in 1986 under the stock symbol SUNW, the symbol was changed in 2007 to JAVA, Sun stated that the brand awareness associated with its Java platform better represented the companys current strategy. Suns logo, which features four interleaved copies of the sun in the form of a rotationally symmetric ambigram, was designed by professor Vaughan Pratt. The initial version of the logo was orange and had the sides oriented horizontally and vertically, but it was rotated to stand on one corner and re-colored purple. In the dot-com bubble, Sun began making more money. It also began spending more, hiring workers and building itself out. Some of this was because of demand, but much was from web start-up companies anticipating business that would never happen. Sales in Suns important hardware division went into free-fall as customers closed shop, several quarters of steep losses led to executive departures, rounds of layoffs, and other cost cutting. In December 2001, the fell to the 1998, pre-bubble level of about $100. But it kept falling, faster than many other tech companies, a year later it had dipped below $10 but bounced back to $20
9.
Subtitle (captioning)
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The encoded method can either be pre-rendered with the video or separate as either a graphic or text to be rendered and overlaid by the receiver. Teletext subtitle language follows the audio, except in multi-lingual countries where the broadcaster may provide subtitles in additional languages on other teletext pages. EIA-608 captions are similar, except that North American Spanish stations may provide captioning in Spanish on CC3, DVD and Blu-ray only differ in using run-length encoded graphics instead of text, as well as some HD DVB broadcasts. Sometimes, mainly at festivals, subtitles may be shown on a separate display below the screen. Television subtitling for the deaf and hard of hearing is referred to as closed captioning in some countries. The word subtitle is the prefix followed by title. In some cases, such as opera, the dialog is displayed above the stage in what are referred to as surtitles. Today, professional subtitlers usually work with specialized software and hardware where the video is digitally stored on a hard disk. Besides creating the subtitles, the subtitler usually also tells the computer software the exact positions where each subtitle should appear and disappear, for cinema film, this task is traditionally done by separate technicians. The end result is a file containing the actual subtitles as well as position markers indicating where each subtitle should appear and disappear. These markers are based on timecode if it is a work for electronic media. For multimedia-style Webcasting, check, SMIL Synchronized Multimedia Integration Language, same-language captions, i. e. without translation, were primarily intended as an aid for people who are deaf or hard of hearing. Internationally, there are several studies which demonstrate that same-language captioning can have a major impact on literacy. This method of subtitling is used by television broadcasters in China. Same Language Subtitling is the use of Synchronized Captioning of Musical Lyrics as a Repeated Reading activity, the basic reading activity involves students viewing a short subtitled presentation projected onscreen, while completing a response worksheet. Closed captioning is the American term for closed subtitles specifically intended for people who are deaf and these are a transcription rather than a translation, and usually contain descriptions of important non-dialog audio as well such as or and lyrics. From the expression closed captions the word caption has in recent years come to mean a subtitle intended for the hard of hearing, be it open or closed. In British English subtitles usually refers to subtitles for the hard of hearing, however, programs such as news bulletins, current affairs programs, sport, some talk shows and political and special events utilize real time or online captioning
10.
BBC One
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BBC One is the flagship television channel of the British Broadcasting Corporation in the United Kingdom, Isle of Man and Channel Islands. It was launched on 2 November 1936 as the BBC Television Service and it was renamed BBC TV in 1960, using this name until the launch of sister channel BBC2 in 1964, whereupon the BBC TV channel became known as BBC1, with the current spelling adopted in 1997. The channels annual budget for 2012–13 is £1.14 billion, the channel is funded by the television licence fee together with the BBCs other domestic television stations, and therefore shows uninterrupted programming without commercial advertising. It is currently the most watched channel in the United Kingdom, ahead of its traditional rival for ratings leadership. As of June 2013 the channel controller for BBC One is Charlotte Moore, the BBC began its own regular television programming from the basement of Broadcasting House, London, on 22 August 1932. BBC Television returned on 7 June 1946 at 15,00, Jasmine Bligh, one of the original announcers, made the first announcement, saying, Good afternoon everybody. Do you remember me, Jasmine Bligh, the Mickey Mouse cartoon of 1939 was repeated twenty minutes later. The competition quickly forced the channel to change its identity and priorities following a reduction in its audience. The 1962 Pilkington Report on the future of broadcasting noticed this, and it therefore decided that Britains third television station should be awarded to the BBC. The station, renamed BBC TV in 1960, became BBC1 when BBC2 was launched on 20 April 1964 transmitting an incompatible 625-line image on UHF. The only way to all channels was to use a complex dual-standard 405- and 625-line, VHF and UHF, receiver. Old 405-line-only sets became obsolete in 1985, when transmission in the standard ended, although standards converters have become available for enthusiasts who collect, BBC1 was based at the purpose-built BBC Television Centre at White City, London between 1960 and 2013. In the weeks leading up to 15 November 1969, BBC1 unofficially transmitted the occasional programme in its new colour system, to test it. At midnight on 15 November, simultaneously with ITV and two years after BBC2, BBC1 officially began 625-line PAL colour programming on UHF with a broadcast of a concert by Petula Clark, colour transmissions could be received on monochrome 625-line sets until the end of analogue broadcasting. In terms of share, the most successful period for BBC1 was under Bryan Cowgill between 1973 and 1977, when the channel achieved an average audience share of 45%. On 30 December 1980, the BBC announced their intention to introduce a new breakfast television service to compete with TV-am. On 17 January 1983, the first edition of Breakfast Time was shown on BBC One, becoming the first UK wide breakfast television service and continued to lead in the rating until 1984. The first major overhaul was to axe the deeply unpopular Sixty Minutes current affairs programme and its replacement was the BBC Six OClock News, a straight new programme in a bid to shore up its failing early evening slot
11.
10 Gigabit Ethernet
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10 Gigabit Ethernet is a group of computer networking technologies for transmitting Ethernet frames at a rate of 10 gigabits per second. It was first defined by the IEEE802. 3ae-2002 standard, half duplex operation and repeater hubs do not exist in 10GbE. Like previous versions of Ethernet, 10GbE can use either copper or fiber cabling, however, because of its bandwidth requirements, higher-grade copper cables are required, category 6a or Class F/Category 7 cables for lengths up to 100 meters. The 10 Gigabit Ethernet standard encompasses a number of different physical layer standards, a networking device, such as a switch or a network interface controller may have different PHY types through pluggable PHY modules, such as those based on SFP+. At the time that the 10 Gigabit Ethernet standard was developed, the WAN PHY encapsulates Ethernet packets in SONET OC-192c frames and operates at a slightly slower data-rate than the local area network PHY. Over the years the Institute of Electrical and Electronics Engineers 802.3 working group has published several standards relating to 10GbE, to implement different 10GbE physical layer standards, many interfaces consist of a standard socket into which different PHY modules may be plugged. Physical layer modules are not specified in a standards body. Relevant MSAs for 10GbE include XENPAK, XFP and SFP+, when choosing a PHY module, a designer considers cost, reach, media type, power consumption, and size. A single point-to-point link can have different MSA pluggable formats on either end as long as the 10GbE optical or copper port type inside the pluggable is identical, XENPAK was the first MSA for 10GE and had the largest form factor. X2 and XPAK were later competing standards with smaller form factors, X2 and XPAK have not been as successful in the market as XENPAK. XFP came after X2 and XPAK and it is also smaller, the newest module standard is the enhanced small form-factor pluggable transceiver, generally called SFP+. Based on the small form-factor pluggable transceiver and developed by the ANSI T11 fibre channel group, it is smaller still, SFP+ has become the most popular socket on 10GE systems. SFP+ modules do only optical to electrical conversion, no clock and data recovery, SFP+ modules share a common physical form factor with legacy SFP modules, allowing higher port density than XFP and the re-use of existing designs for 24 or 48 ports in a 19 rack width blade. Optical modules are connected to a host by either a XAUI, XENPAK, X2, and XPAK modules use XAUI to connect to their hosts. XAUI uses a data channel and is specified in IEEE802.3 Clause 48. XFP modules use a XFI interface and SFP+ modules use an SFI interface, XFI and SFI use a single lane data channel and the 64b/66b encoding specified in IEEE802.3 Clause 49. SFP+ modules can further be grouped into two types of host interfaces, linear or limiting, limiting modules are preferred except when using old fiber infrastructure which requires the use of the linear interface provided by 10GBASE-LRM modules. There are two classifications for optical fiber, single-mode and multi-mode, in SMF light follows a single path through the fiber while in MMF it takes multiple paths resulting in differential mode delay
12.
Video on demand
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IPTV technology is often used to bring video on demand to televisions and personal computers. Internet television, using the Internet, is a popular form of video on demand. VOD can also be accessed via desktop client applications such as the Apple iTunes online content store, some airlines offer VOD as in-flight entertainment to passengers through individually controlled video screens embedded in seatbacks or armrests or offered via portable media players. Some video on demand services such as Netflix use a model that requires users to pay a monthly fee to access a bundled set of content. Other services use a model, where access is free for Internet users. Downloading and streaming video on demand systems provide the user all of the features of Portable media players. Some VOD systems that store and stream programs from hard drives use a memory buffer to allow the user to fast forward. It is possible to put video servers on local area networks, streaming video servers can also serve a wider community via a WAN, in which case the responsiveness may be reduced. Download VOD services are practical to homes equipped with cable modems or DSL connections, servers for traditional cable and telco VOD services are usually placed at the cable head-end serving a particular market as well as cable hubs in larger markets. In the telco world, they are placed in either the central office, the first Video on Demand systems used tapes as the realtime source of video streams. GTE started as a trial in 1990 with AT&T providing all components, by 1992 VOD servers were supplying previously encoded digital video from disks and DRAM. In the US the 1982 anti-trust break-up of AT&T resulted in a number of telephone companies called Baby Bells. Following this the Cable Communications Policy Act of 1984 prohibited telephone companies from providing services within their operating regions. All of these companies and others began holding trials to setup systems for supplying Video on Demand over telephone, in November 1992 Bell Atlantic announced a VOD trial. The IBM was developing video server code-named Tiger Shark, concurrently Digital Equipment was developing a scalable video server. Bell Atlantic selected IBM and April 1993 the system became the first VOD over ADSL to be deployed outside the lab, in 1994-5 US West went on to file for VOD at several cities. 330,000 subscribers in Denver,290,000 in Minneapolis, many VOD trials were held with various combinations of server, network and set-top. Of these the primary players in the US were the companies, using DEC, Microsoft, Oracle, IBM, Hewlett-Packard, USA Video, nCube, SGI
