title: London Stock Exchange Group

text: Between April and May 2006, having been rebuffed in an informal approach, Nasdaq built up a 23% stake in the Exchange. The stake grew to 29% as a result of the London exchange's share consolidation. Nasdaq has since sold its investment.


title: London Stock Exchange Group

text: In 2007, the Exchange acquired the Milan-based Borsa Italiana for €1.6bn (£1.1bn; US$2bn) to form the London Stock Exchange Group plc. The combination was intended to diversify the LSE's product offering and customer base. The all-share deal diluted the stakes of existing LSE shareholders, with Borsa Italiana shareholders receiving new shares representing 28 per cent of the enlarged register.


title: London Stock Exchange Group

text: On 16 September 2009, the London Stock Exchange Group agreed to acquire Millennium Information Technologies, Ltd., a Sri Lankan-based software company specialising in trading systems, for US$30m (£18m). The acquisition was completed on 19 October 2009.


title: London Stock Exchange Group

text: On 9 February 2011, TMX Group, operator of the Toronto Stock Exchange agreed to join forces with the London Stock Exchange Group in a deal described by TMX head Tom Kloet as a 'merger of equals' (though 8/15 board members of the combined entity will be appointed by LSE, 7/15 by TMX). The deal, subject to government approval would create the world's largest exchange operator for mining stocks. In the UK, the LSE Group first announced it as a takeover, however in Canada the deal was reported as a merger. The provisional name for the combined group would be LTMX Group plc. On 13 June 2011, a rival, and hostile bid from the "Maple Group" of Canadian interests, was unveiled for the TMX Group. This was a cash and stock bid of , launched in the hope of blocking the LSE Group's takeover of TMX. The group was composed of the leading banks and financial institutions of Canada. The London Stock Exchange however announced it was terminating the merger with TMX on 29 June 2011 citing that "LSEG and TMX Group believe that the merger is highly unlikely to achieve the required two-thirds majority approval at the TMX Group shareholder meeting".


title: London Stock Exchange Group

text: On 2 June 2014, the LSE became the 10th stock exchange to join the United Nations' Sustainable Stock Exchanges (SSE) initiative.


title: London Stock Exchange Group

text: On 26 June 2014, the LSE announced it had agreed to buy Frank Russell Co., making it one of the largest providers of index services.


title: London Stock Exchange Group

text: In January 2015, Reuters reported that the London Stock Exchange Group planned to put Russell Investments up for sale, and estimates the sale will produce $1.4 billion.


title: London Stock Exchange Group

text: In March 2016, the company announced it had reached an agreement with Deutsche Börse to merge. The companies would have been brought under a new holding company, UK TopCo, and would retain both headquarters in London and Frankfurt. On 25 February 2017, the London Stock Exchange Group PLC stated it wouldn't sell its fixed-income trading platform in Italy to Deutsche Börse AG, to appease anti-trust concerns. The planned merger between the two exchanges, which was estimated to create the largest exchange in Europe, was subsequently described as "at risk" by "the Wall Street Journal". The merger attempt was blocked by EU Competition Regulator on 29 March 2017 stating that "The Commission's investigation concluded the merger would have created a de facto monopoly in the markets for clearing fixed income instruments".


title: London Stock Exchange Group

text: In August 2019, the company agreed to buy Refinitiv in an all-share transaction valuing the target at $27 billion. Shortly thereafter, on 11 September 2019, LSEG itself became the target of a £32 billion bid by the Hong Kong Exchanges and Clearing, subject to abandoning its plans to buy Refinitiv. LSEG rejected the takeover bid two days later. In order to secure the Refinitiv deal, in July 2020, LSEG announced that it was considering selling its Italian assets including MTS, Italian bond trading venue and potentially Borsa Italiana.


title: London Stock Exchange Group

text: On 18 September 2020, LSEG entered into exclusive talks to sell the Italian Bourse to Euronext. The acquisition was announced on 9 October of that same year and was completed on 29 April 2021.


title: London Stock Exchange Group

text: The positions of Chairman and Chief Executive of the London Stock Exchange Group were founded in 2007, upon the establishment of the Group. This is not to be confused with the Chairmen and Chief Executive's of the London Stock Exchange plc, which is a subsidiary of the Group. The current Chief Executive is former Goldman Sachs banker David Schwimmer, who was appointed in 2018, replacing Xavier Rolet, who was ousted in November 2017. Schwimmer's most recent role at Goldman Sachs was serving as "global head of market structure and global head of metals and mining in investment banking".


title: London Stock Exchange Group

text: Following the merger with Borsa Italiana, the group is Europe's leading equities business, with 48% of the FTSEurofirst 100 by market capitalisation and with the most liquid order book by value and volume traded. Its activities include:


title: Nick Vallelonga

text: Nicholas Anthony Vallelonga (born September 13, 1959) is an American actor and filmmaker. He is best known for co-writing and producing the film "Green Book", for which he received two Academy Awards for Best Original Screenplay and Best Picture. He also won two Golden Globes in the same categories, as well as the PGA Award for Best Film. He has also directed the films "In the Kingdom of the Blind, the Man with One Eye Is King", "Choker" and "Stiletto", and co-wrote the screenplay to "Deadfall".


title: Nick Vallelonga

text: Vallelonga was born in 1959, the son of Tony and Dolores Vallelonga. He had a younger brother, Frank, who died in November 2022. He initially followed his father into acting, with minor roles in films including "The Godfather", "Splash", "Goodfellas", and "Prizzi's Honor". He made his screenwriting debut with "Deadfall", directed by Christopher Coppola. While continuing his acting career, he continued to write and direct various independent films, such as "A Brilliant Disguise", "The Corporate Ladder", "Choker", "Stiletto", and "Yellow Rock".


title: Nick Vallelonga

text: Vallelonga achieved prominence with "Green Book", which he co-wrote and produced. Based on the friendship of his father and Don Shirley, "Green Book" was critically praised and received dozens of award nominations, although the film was not without controversy, as Shirley's family accused Vallelonga of falsifying information in the movie. In "Variety", Vallelonga disputed the allegations: "There's a lot of information [the Shirley family] doesn't have, and they were hurt that I didn't speak to them. But to be quite honest with you, Don Shirley himself told me not to speak to anyone. And he only wanted certain parts of his life … So obviously, to say I didn't contact them, that was hard for me because I didn't want to betray what I promised him."


title: Nick Vallelonga

text: In 2019, Vallelonga apologized for a 2015 tweet that agreed with Donald Trump's claim that Muslims in Jersey City cheered when the World Trade Center towers collapsed.


title: 1996–97 NBA season

text: The 1996–97 NBA season was the 51st season of the National Basketball Association (NBA). The league used this season to celebrate its 50th anniversary, which included the unveiling of the league's list of its 50 greatest players. This particular season featured what has since been acknowledged as one of the most talented rookie-classes, featuring the debuts of Allen Iverson, Ray Allen, Kobe Bryant, Steve Nash, Jermaine O'Neal, Ben Wallace and Stephon Marbury. The season ended with the Chicago Bulls defeating the Utah Jazz 4 games to 2 in the NBA Finals to win the franchise's 5th championship.


title: 1996–97 NBA season

text: The 1996 NBA lockout was the second lockout of four in the history of the NBA. It began and ended on July 10, 1996. The lockout was imposed after the league and the players union could not reach an agreement involving $50 million in profit sharing from television revenue. The league requested 50 percent of the profits be applied toward player salaries while the union pushed for a larger share. After a few hours of talks, the league agreed to allocate an additional $14 million per season in television revenue toward the salary cap during the last four years of the six-year collective bargaining agreement. The agreement ending the lockout was announced a few hours after the lockout began.


title: 1996–97 NBA season

text: Teams in bold advanced to the next round. The numbers to the left of each team indicate the team's seeding in its conference, and the numbers to the right indicate the number of games the team won in that round. The division champions are marked by an asterisk. Home court advantage does not necessarily belong to the higher-seeded team, but instead the team with the better regular season record; teams enjoying the home advantage are shown in italics.


title: Twentynine Palms, California

text: Twentynine Palms (also known as 29 Palms) is a city in San Bernardino County, California. Twentynine Palms serves as one of the entry points to Joshua Tree National Park.


title: Twentynine Palms, California

text: Twentynine Palms was named for the palm trees found there in 1852 by Col. Henry Washington while surveying the San Bernardino base line. A post office was established in 1927.


title: Twentynine Palms, California

text: A road named Utah Trail honors the late 1800s pioneers on a trail originating in Utah (reportedly Saint George) that went to Twentynine Palms.


title: Twentynine Palms, California

text: Joshua Tree National Park, which lies just to the south of Twentynine Palms, was designated a national monument in 1936, and became a national park in 1994. The nearby Marine Corps Air Ground Combat Center Twentynine Palms was founded in 1952.


title: Twentynine Palms, California

text: At the 2010 census, there were 25,048 people in 8,095 households, including 5,847 families, in the city. The population density was . There were 9,431 housing units at an average density of 159.5 per square mile, of the occupied units 2,742 (33.9%) were owner-occupied and 5,353 (66.1%) were rented. The homeowner vacancy rate was 3.6%; the rental vacancy rate was 9.2%. 6,876 people (27.5% of the population) lived in owner-occupied housing units and 14,825 people (59.2%) lived in rental housing units. The racial makeup of the city was 71.6%, White (60.8% non-Hispanic), 8.2% African American, 1.3% Native American, 3.9% Asian, 1.4% Pacific Islander, 6.7% from other races, and 6.9% from two or more races. Hispanic or Latino of any race were 20.8% of the population.


title: Twentynine Palms, California

text: The census reported that 21,701 people (86.6% of the population) lived in households, and 3,347 (13.4%) lived in non-institutionalized group quarters.


title: Twentynine Palms, California

text: Of the 8,095 households 43.3% had children under the age of 18 living in them, 54.5% were opposite-sex married couples living together, 12.9% had a female householder with no husband present, 4.9% had a male householder with no wife present. There were 5.0% unmarried opposite-sex partnerships, and 1.6% same-sex married couples or partnerships. 21.1% of households were one person and 5.6% were one person aged 65 or older. The average household size was 2.68 and the average family size was 3.10.


title: Twentynine Palms, California

text: The age distribution was 25.6% under the age of 18, 30.0% aged 18 to 24, 25.5% aged 25 to 44, 13.1% aged 45 to 64, and 5.8% who were 65 or older. The median age was 23.5 years. For every 100 females, there were 129.0 males. For every 100 females age 18 and over, there were 139.9 males.


title: Twentynine Palms, California

text: The median household income was $42,572. About 14.4% of the population were living below the poverty line.


title: Twentynine Palms, California

text: At the 2000 census there were 14,764 people in 5,653 households, including 3,855 families, in the city. The population density was 269.3 inhabitants per square mile (104.0/km). There were 6,952 housing units at an average density of . The racial makeup of the city was 71.0% White, 9.4% African American, 1.5% Native American, 3.8% Asian, 10.2% Pacific Islander, 6.2% from other races, and 6.4% from two or more races. Hispanic or Latino of any race were 14.9%.


title: Twentynine Palms, California

text: Of the 5,653 households 39.1% had children under the age of 18 living with them, 49.8% were married couples living together, 13.7% had a female householder with no husband present, and 31.8% were non-families. 25.1% of households were one person and 7.4% were one person aged 65 or older. The average household size was 2.6 and the average family size was 3.1.


title: Twentynine Palms, California

text: The age distribution was 31.2% under the age of 18, 15.2% from 18 to 24, 28.4% from 25 to 44, 16.7% from 45 to 64, and 8.6% 65 or older. The median age was 27 years. For every 100 females, there were 101.8 males. For every 100 females age 18 and over, there were 98.7 males.


title: Twentynine Palms, California

text: The median household income was $31,178 and the median family income was $32,251. Males had a median income of $25,081 versus $25,141 for females. The per capita income for the city was $14,613. About 13.6% of families and 16.8% of the population were below the poverty line, including 25.3% of those under age 18 and 10.0% of those age 65 or over.


title: Twentynine Palms, California

text: The city is located in the Mojave Desert in Southern California. It lies on the northern side of the Joshua Tree National Park and includes one of the entrances to the park, at the Oasis of Mara.


title: Twentynine Palms, California

text: According to the United States Census Bureau, the city has a total area of , all land. The city is at an elevation of . The Marine Corps Air Ground Combat Center Twentynine Palms is located there.


title: Twentynine Palms, California

text: Due in large part to its elevation of more than above sea level, Twentynine Palms has a slightly cooler climate, especially during winter, than Palm Springs, but with essentially the same subtropical desert characteristics. On average, temperatures reach on 89 days, on 154 days, and the freezing mark on 17 nights annually. Extremes range from on December 23, 1990, to on July 11, 1961. Winters are moderately cool, with highs in the 60s °F and lows in the 40s °F. Summers are hot, with high temperatures above . The wettest month is August, with inches of rain, mostly from monsoon thunderstorms.


title: Twentynine Palms, California

text: The city uses a council-manager form of government. An elected city council establishes policy and appoints a city manager who executes these policies.


title: Twentynine Palms, California

text: The Oasis of Mara, the original source of water and the historic source of all economic activity in the area, is divided into two parts. To the east, a long strip of palm trees terminates at the Joshua Tree National Park Visitor's Center, which is visited by approximately 140,000 people every year, and is maintained by the United States National Park Service. To the west, the remainder of the oasis is owned by the 29 Palms Inn, a historic hotel, and ends in a large shaded pond.


title: Twentynine Palms, California

text: The current economy depends largely on the nearby Marine Corps Air Ground Combat Center, as well as tourism associated with Joshua Tree National Park. In February 2015, the city set in place rules governing vacation rentals, and has granted approximately one hundred permits, compared to over one thousand in the nearby community of Joshua Tree.


title: Twentynine Palms, California

text: The city has a series of 26 outdoor murals painted on local buildings featuring various aspects of desert life and history.


title: Twentynine Palms, California

text: The 29 Palms Historical Society, housed in the original schoolhouse of the city, maintains a museum devoted to local history. The Historical Society also hosts an annual "Weed Show" each November devoted to art work composed of weeds. The Twentynine Palms Artists Guild maintains exhibits devoted to local artists.


title: Twentynine Palms, California

text: "The Desert Trail" newspaper in Yucca Valley is published weekly. "The Sun Runner Magazine of California Desert Life and Culture" is published bi-monthly.


title: Twentynine Palms, California

text: There are two TV stations: K15FC-D (KESQ-TV (ABC), KPSP (CBS), KDFX (Fox), KCWQ-LD (CW) and KUNA-LD (Telemundo) subchannels) and KPSE-LD (My Network) 29 (also KMIR-TV (NBC), ION, MeTV and Movies! subchannels) from the Riverside County, California TV market, but the area is actually part of the Palm Springs TV market.


title: Twentynine Palms, California

text: There is one AM station: KNWH a transmitter of KNWQ-1140 "KNews" Radio – Twentynine Palms (Inland Empire, California and Coachella Valley radio markets) CA US news/talk, and seven commercial plus two public FM Stations –


title: Twentynine Palms, California

text: On April 22, 1945, "The Jack Benny Program" was broadcast from Twentynine Palms Auxiliary Naval Air Station. There were jokes about the base's dry, hot weather, along with a comedic sketch of the town's history.


title: Baby Bash

text: Ronald Ray Bryant (born October 18, 1969), better known by his stage name Baby Bash (formerly Baby Beesh), is an American rapper. From 1995 until 1998, as part of Dope House Records, after which he changed the last part of his stage name to "Bash." His first album "Savage Dreams" (2001), was followed by "On Tha Cool" (2002), and his first major label release: "Tha Smokin' Nephew" (2003). The album included the single "Suga Suga" (alongside Frankie J), which peaked at number 7 on the "Billboard" Hot 100.


title: Baby Bash

text: In 2005, "Super Saucy" was released, preceded by the lead single "Baby, I'm Back" (featuring Akon). "Cyclone" followed in 2007, with its title single (featuring T-Pain) and its follow-up, "What Is It" (featuring Sean Kingston), finding moderate success on the "Billboard" charts as well.


title: Baby Bash

text: He contributed to other performers' works, including the song "Obsession (No Es Amor)" by the 3rd Wish, released in Europe and later a U.S release with a re-recording of the European version, performed by Frankie J in 2005 and "Doing Too Much" by Paula DeAnda in 2006.


title: Baby Bash

text: He has collaborated with numerous other artists during his career, such as West Coast rappers B-Legit, C-Bo, Coolio, E-40 and Mac Dre, R&B singers like Akon, Avant, Natalie, Bohemia, Mario, and Nate Dogg, and other Latino rappers such as Fat Joe, Nino B, Doll-E Girl, South Park Mexican, Frost, and Pitbull. He continues to write lyrics for singers such as Paula DeAnda, Jennifer Hudson and Frankie J.


title: Baby Bash

text: Bryant was born in Vallejo, California to a Mexican mother from Mendota, California. Bryant was raised by his grandmother, and Bryant's father and uncles exposed him to many different types of musical genres. Initially, Bryant wanted to be a professional basketball player. He planned to play basketball for the junior college he attended in California during the mid-1990s. An ankle injury prevented Bryant from pursuing basketball as a career.


title: Baby Bash

text: Bryant's music career began as part of the group Potna Duece in Vallejo, California. He went to Houston in 1998, where he met fellow rapper South Park Mexican. Prior to his success as a solo artist he, under the name "Baby Beesh", was part of rap groups Potna Deuce and Latino Velvet.


title: Baby Bash

text: Bash's debut album, "Savage Dreams", was released on the independent label Dope House Records in 2001. The album features guest performances by South Park Mexican, Frost, Jay Tee, Mr. Kee, Don Cisco and Merciless.


title: Baby Bash

text: "On tha Cool" is his second studio album, released June 11, 2002, on Dope House Records. It was produced by Happy P and Johnny Z. The album features guest performances by SPM, Jay Tee, Russell Lee, Don Cisco, Mr. Shadow and DJ Kane.


title: Baby Bash

text: The acclaim he received caught the attention of Universal Records, who signed him later that year. In 2003, Baby Bash released his first album on a major label, "Tha Smokin' Nephew". It debuted at number 48 on the Billboard 200. Five months after its release, the album was certified Gold by the RIAA. As of March 2005, the album has sold 531,000 copies in the United States. "Ménage à Trois" is an independent label album (fifth album overall) by Baby Bash.


title: Baby Bash

text: In 2005, Bash released "Super Saucy". "Super Saucy" is the first official studio album (sixth album overall) by Baby Bash released in March 2005. It spawned the hit single, "Baby I'm Back" (featuring Akon) which reached number 19 on the Billboard Hot 100. It is also his last release on Universal Records before signing with Arista Records. The album debuted at number 11 on the Billboard 200 with 48,000 copies sold in the first week released, becoming Baby Bash's highest-charting album to date.


title: Baby Bash

text: He was featured on Paula DeAnda's first single "Doin' Too Much", from her debut album "Paula DeAnda". His third studio album, "Cyclone" (initially titled "Ronnie Rey All Day"), was released in late October 2007. So far, Bryant has released three singles from the album: "Mamacita", featuring Marcos Hernandez, "Na Na", and "Cyclone", featuring Mickaël & T-Pain. During the month of the album's release, Baby Bash became Myspace's #1 Latin artist, and the single "Cyclone" sold over 750,000 digital copies and ringtones prior to the album's release.


title: Baby Bash

text: Bryant completed a film entitled "Primos", starring Chingo Bling and Danny Trejo. The comedy involves three cousins working in a bakery with dreams of making money and was released in 2010. His major-label debut, "Tha Smokin' Nephew", was well received by AllMusic, but his 2007 album, "Cyclone", was given mixed reviews, including a negative review by "Rolling Stone" magazine.


title: Baby Bash

text: "Bashtown" is the fourth studio album by Bryant. Released on March 22, 2011, it is the first album to be released on Upstairs Records. "Bashtown" features production from Jim Jonsin, Printz Board, Happy P, Mickaël, J. Lacy, and C-Ballin, and features vocal guests E-40, Paul Wall, Slim Thug, and Lloyd, among others. According to Bryant, the album was recorded in 2010.


title: Baby Bash

text: In December 2010, Bryant was offered a job as an on-air personality for Wild 94.9, a Rhythmic Contemporary commercial radio station in San Francisco, California. In the same month, Bryant announced that he would be endorsing a new energy drink for women named after his 2011 single "Go Girl". Part of the sales proceeds from the energy drink will be donated to various charities for breast cancer- and ovarian cancer-research for women.


title: Baby Bash

text: Bryant was arrested with Paul Wall on the night of September 10, 2011, in El Paso, Texas, for possession of marijuana. Both rappers were released the same night on US$300 bail.


title: Baby Bash

text: On December 17, 2013, Bryant released his eighth studio album, "Unsung". The album features artists such as Too Short, Miguel, and Problem. Production credits of the album belong to DJ Rex, Happy Perez, Mickaël, J. Lacy, and C-Ballin.


title: Wintergreen

text: Wintergreen is a group of aromatic plants. The term "wintergreen" once commonly referred to plants that remain green (continue photosynthesis) throughout the winter. The term "evergreen" is now more commonly used for this characteristic.


title: Wintergreen

text: Most species of the shrub genus "Gaultheria" demonstrate this characteristic and are called wintergreens in North America, the most common generally being the American wintergreen ("Gaultheria procumbens"). Wintergreens in the genus "Gaultheria" contain an aromatic compound, methyl salicylate, and are used as a mintlike flavoring.


title: Wintergreen

text: Wintergreen is a common flavoring in American products ranging from chewing gum, mints, and candies to smokeless tobacco such as dipping tobacco (American "dip" snuff) and snus. It is a common flavoring for dental hygiene products such as mouthwash and toothpaste. It is often a component of the American-origin drink root beer.


title: Wintergreen

text: Wintergreen oil is an ingredient in some vegetable-oil based lubricants used in firearm maintenance. These products, sold under the names Seal1 and Frog Lube, are proprietary blends of vegetable oils intended to clean, lubricate and preserve the metal surfaces of firearms. They have the advantages over petroleum-based products of being non-toxic and biodegradable.


title: Wintergreen

text: Artificial wintergreen oil, which is pure methyl salicylate, is used in microscopy because of its high refractive index. Natural wintergreen oil can be distinguished from artificial by gas chromatography (GC) and GC isotope ratio mass spectrometry analysis.


title: Wintergreen

text: The "Gaultheria" species share the common characteristic of producing oil of wintergreen. Wintergreen oil is a pale yellow or pinkish fluid liquid that is strongly aromatic with a sweet, woody odor (components: methyl salicylate (about 98%), α-pinene, myrcene, delta-3-carene, limonene, 3,7-guaiadiene, and delta-cadinene) that gives such plants a distinctive "medicinal" smell whenever bruised. Salicylate sensitivity is a common adverse reaction to the methyl salicylate in oil of wintergreen; it can produce allergy-like symptoms or asthma.


title: Wintergreen

text: Wintergreen essential oil is usually obtained by steam distillation of the leaves of the plant following maceration in warm water. Methyl salicylate is not present in the plant until formed by enzymatic action from a glycoside within the leaves as they are macerated in warm water. Oil of wintergreen is also manufactured from some species of birch, but these deciduous trees are not called wintergreens. "Spiraea" plants also contain methyl salicylate in large amounts and are used similarly to wintergreen. Wintergreen has a strong "minty" odor and flavor; however, the "Gaultheria"-genus plants are not true mints, which belong to the genus "Mentha."


title: Wintergreen

text: Wintergreen also is used in some perfumery applications and as a flavoring agent for toothpaste, chewing gum, soft drinks, confectionery, Listerine, and mint flavorings. Wintergreen is used for rust removal and degreasing of machinery and is particularly effective for breaking through sea water corrosion.


title: Wintergreen

text: One milliliter (20 drops) of wintergreen oil is equivalent to about 1860 mg of aspirin, or almost six regular-strength adult aspirin tablets.


title: Wintergreen

text: Treatment is identical to the other salicylates. Early use of hemodialysis in conjunction with maximal supportive measures is encouraged in any significant ingestion of methyl salicylate.


title: Safety car

text: In motorsport, a safety car, or a pace car, is an automobile which limits the speed of competing cars or motorcycles on a racetrack in the case of a "caution period" such as an obstruction on the track or bad weather. The aim of the safety car is to enable the clearance of any obstruction under safer conditions, especially for marshals and/or await more favourable track conditions weather-wise.


title: Safety car

text: During a caution period the safety car (which generally consists of an aptly modified high-performance production car) enters the track ahead of the leader. Depending on the regulations in effect, competitors are not normally allowed to pass the safety car or other competitors during a caution period, and the safety car leads the field at a pre-determined safe speed, which may vary by series and circuit. At the end of the caution period, the safety car leaves the track and the competitors resume normal racing. The first reliance on this safety measure occurred with the deployment of a pace car during the inaugural Indianapolis 500 in 1911.


title: Safety car

text: The use of a safety car has the effect of bunching competitors together, such as to eliminate any time and distance advantage that a leading driver may have had over the remaining field of competitors. This effect can make racing more competitive upon full race resumption; conversely, it has also contributed to faster leading drivers being negated just rewards for their efforts prior to the caution period.


title: Safety car

text: Subject to the racing regulations in force, it is not uncommon for drivers to be allowed to make pitstops during safety car periods. This situation may provide a strategic advantage since any scheduled refueling, tire change or maintenance may be carried out while other competitors are lapping at lower speed, and the drivers who pit then simply rejoin a queue of cars all running together. During normal racing conditions, such interventions would typically involve losing significant terrain over those drivers that remain on-track.


title: Safety car

text: Another notable effect of safety car periods is that racing cars consume less fuel until full race resumption, which can allow competitors to run longer distances on a tank of fuel than would otherwise have been possible and/or reduce the number of pitstops required for the duration of the race.


title: Safety car

text: In Formula One if an accident or inclement weather (typically, heavy rain) prevents normal racing from continuing safely, the Race Director will call for a "safety car" period, which would see marshals wave yellow flags and hold "SC" boards, pending the car in question entering the track. From 2007, all Formula One cars must have LEDs and/or displays fitted to the steering wheel or cockpit, which inform the driver which flags are being waved. A yellow LED is illuminated when the safety car is deployed.


title: Safety car

text: The safety car has both orange and green lights mounted on its roof in the form of a light bar. The green lights are used to signal that it is possible to overtake the safety car; this is only done until the race leader is immediately behind the safety car and at the head of the queue of race cars following.


title: Safety car

text: From 2015, the safety car is not required to wait until all backmarkers have caught back up to the queue. When the safety car is ready to leave the circuit, it will turn off its orange lights to indicate that it will enter the pit lane at the end of the lap. Drivers must continue in formation until they cross the first safety car line, where circuit green lights and flags will indicate they are free to race again.


title: Safety car

text: The safety car is piloted by professional drivers (since 2000, by Bernd Mayländer) on-board high-powered modified vehicles supplied by Mercedes-Benz and Aston Martin (the latter since the 2021 season), and must maintain a reasonable speed so as to ensure that the competitors' tyres are as close as possible to operating temperature and their engines do not overheat. The driver of the safety car is accompanied by a co-driver to assist with operations and communications.


title: Safety car

text: For incidents during the first three laps, the safety car also has an advantage over the traditional red flag; with a red flag, it would take a minimum of fifteen minutes to restart the race, and the two-hour limit would not start until the cars were ready for a second formation lap. With regards to the time limit, the race is being scored and the time is also counting while the safety car is on the track, and the race resumes.


title: Safety car

text: The first use of a safety car in Formula One is reported to have taken place at the 1973 Canadian Grand Prix, where a yellow Porsche 914 was called for duty following various incidents under treacherous weather conditions. Controversially, on that occasion, it took several hours after the race to figure out the winner and final results since the safety car driver had placed his car in front of the wrong competitor thus causing part of the field to be one lap down incorrectly.


title: Safety car

text: The sport officially introduced safety cars in , after trials were conducted at both the French and British Grands Prix during the preceding season. Since , as part of promotional arrangements, the main supplier of safety cars has been Mercedes-Benz, with Aston Martin sharing the duties with them from , unlike previous years that have seen cars of different brands being used throughout the season and depending on the track visited (for example, the exotic Lamborghini Countach for the Monaco Grand Prix in the 1980s and the Lamborghini Diablo for the 1995 Canadian Grand Prix to the more mundane Fiat Tempra used at the rain-affected 1993 Brazilian Grand Prix and the high performance version of the Opel Vectra used at the infamous 1994 San Marino Grand Prix.


title: Safety car

text: From , new procedures were applied for the first time during the Bahrain Grand Prix. The pit lane was closed immediately upon the deployment of the safety car. No car could enter the pits until all cars on the track had formed up in a line behind the safety car, they passed the pit entrance, and the message "pit lane open" was given. A ten-second stop/go penalty (which must be taken when the race is resumed) was imposed on any driver who entered the pit lane before the pit lane open message is given. However, any car which was in the pit entry or pit lane when the safety car was deployed would not incur a penalty.


title: Safety car

text: From , however, this procedure has been dropped, and replaced by software that calculates where a car is on the track and a minimum lap time it should take the car to get to the pits. Cars that enter the pits before this time limit has expired are penalised.


title: Safety car

text: When the safety car and the drivers behind it are on the start/finish straight, there is a red light at the exit of the pit lane. Drivers who go past the red light are disqualified from the race. This has happened to several drivers during the years, such as Juan Pablo Montoya at the 2005 Canadian Grand Prix and Giancarlo Fisichella and Felipe Massa in the 2007 Canadian Grand Prix. At the same race a year later, Lewis Hamilton failed to notice the red light and slammed into the back of the car of Kimi Räikkönen, who was waiting at the end of the pit lane alongside Robert Kubica.


title: Safety car

text: From , once cars were lined up behind the safety car, lapped cars were no longer allowed to unlap themselves before the race was restarted. This rule was abandoned from the season onwards, with cars now allowed to unlap themselves before the race resumes. However, since , the safety car does not need to wait for the backmarkers to catch up with the leading pack before returning to the pits.


title: Safety car

text: The 2021 Belgian Grand Prix infamously became the shortest race in Formula One World Championship history and the first (and so far only) World Championship Grand Prix in history to be run entirely behind the safety car with no running taking place under green flag conditions, with two full laps completed behind the safety car before the race was red flagged on lap 3 and not restarted thereafter with results taken from the end of lap 1 with Max Verstappen declared the winner of the event and half points awarded to the top 10 classified drivers.


title: Safety car

text: In response to the controversial safety car restart at the 2021 Abu Dhabi Grand Prix, the FIA reworked the safety car restart procedure: instead of waiting for the last lapped car to unlap itself, the safety car will now be withdrawn one lap after the instruction to unlap is received.


title: Safety car

text: Since 2021, F1 has featured two official safety cars, both the Aston Martin Vantage and the Mercedes-AMG GT R that was already used in previous seasons. From 2022, Mercedes will provide a Black Series variant of their model.


title: Safety car

text: Following an accident at the 2014 Japanese Grand Prix, which saw driver Jules Bianchi suffer a serious head injury which led to his death, the FIA established an "accident panel" to investigate the dynamics of the accident and ways to minimize the risk of a crash during similar circumstances that do not warrant the deployment of a safety car and cannot be simply managed with yellow flags.


title: Safety car

text: The accident panel recommended the implementation of a "virtual safety car", based on the "slow zone" system used in Le Mans racing. Compared to the former, the safety car does not actually appear on the track. On top of not being allowed to overtake under yellow flag conditions in the affected sector, a "VSC" icon would appear trackside and on the drivers' steering displays, obliging drivers to not exceed the posted speed limit, thus resulting in a 35% speed reduction. The system was similar to the Electro-PACER lights used in the Indianapolis 500 races from 1972 until 1978, except that engine control units (ECU) were involved and could enforce speed limits under the current system.


title: Safety car

text: The VSC was tested over the course of the final three races of the season, during parts of free practice sessions. The system was evolved taking into account drivers' feedback and was officially introduced for the season following ratification by the World Motor Sport Council (WMSC). The VSC was officially used for the first time, and for a brief period prior to the deployment of the actual safety car, at the 2015 Monaco Grand Prix, following a 30G crash involving Max Verstappen. The system saw its first extended deployment at the 2015 British Grand Prix after Carlos Sainz Jr.'s power unit failed at Club Corner of the Silverstone Circuit. All drivers must keep their delta times positive at this point.


title: Safety car

text: The Full Course Yellow condition is the Formula E version of the Virtual Safety Car. In this condition, all marshal posts will wave yellow flags, accompanied by a sign that says "FCY" with a yellow background. This condition is often decided by the Race Director whether it is appropriate to implement it or not. The fans (if they are watching the race on TV) and drivers can hear the Race Director declare the FCY on the radio. Once the FCY is implemented, all drivers must activate the FCY limiter, which, similar to the pit speed limiter, keeps the car under FCY speeds despite the throttle being flat to the floor. Overtaking is not allowed under FCY conditions, but if a driver does overtake another driver, like when Jean-Éric Vergne overtook António Félix da Costa at the 2019 Rome ePrix, the driver who overtook the other driver can be penalised. For season 6 of Formula E, when there is an FCY period, everyone is no longer allowed to activate Attack Mode. For every minute spent under FCY conditions, 1kWh of energy kept in reserve by the drivers will be subtracted, giving more energy saving tactics to the drivers and teams alike. Like Formula One, Formula E does have a safety car condition, but instead of a Mercedes-AMG GT R as the safety car, from 2014 to 2021, a BMW i8 plug-in hybrid sports car was used. Starting with the 2021 Rome ePrix, a Mini Electric was used, and a Porsche Taycan has been used from 2022 onwards. Formula E also includes a rule from 2022 onward which states that if the safety car is used in a race, extra time will be added in order to compensate for the missed racing time due to the safety car.


title: Safety car

text: The first use of a pace car in automobile racing was at the inaugural Indy 500 in 1911. The officials at the Indianapolis Motor Speedway have been selecting a pace car and its driver for the Indy 500 each year since that first race. The first pace car was a Stoddard-Dayton driven by Carl G. Fisher. In recent years Chevrolet models have been chosen as the official pace car, owing to the ability for them to be used at both major automobile races at the Speedway (typically Corvette at the 500 and Impala at the 400). The pace car is selected two months before the race runs, allowing the manufacturer of the selected pace car to produce replicas of that year's car, which sell at a marked premium to collectors and race fans. Pace car replicas are often seen on the streets of Indianapolis weeks before the race is actually held, and a celebrity driver is usually used for the start of the race only.


title: Safety car

text: In the last 50 years, the Pontiac Trans Am, Chevrolet Camaro, Chevrolet Corvette, Oldsmobile Cutlass, and Ford Mustang are the only models that have been selected as pace cars three or more times.


title: Safety car

text: During the IndyCar Series season, however, Johnny Rutherford, Sarah Fisher, and Oriol Servià are the normal drivers of the IRL pace car for all events. The pace car is deployed for debris, collision, or weather reasons. Since 1993, upon the waving of the yellow flag, pit road is closed until the pace car picks up the leader and passes the pit entrance the first time, unless track blockage forces the field to drive through pit lane. Another duty of the pace car is to lead the field around the course on parade laps prior to the start of the race. These increase in speed, allowing for a flying start of the race.


title: Safety car

text: Furthermore, two other rule changes have been implemented. Since 2000, with one lap to go before going back to green, the pace car pulls off the track in turn one rather than in turn four. The current leader of the race is then assigned the task of pacing the field back to the green flag. After much consideration, this rule was added to prevent a situation much like the one that happened in the 1995 Indianapolis 500, when Scott Goodyear passed the pace car going back to green. In 2002, another rule was added. With one lap to go before the green, the pace car waves by all cars (if there are any) between the pace car and the actual leader of the race. This allows for the leader to control the restart without lapped cars being in front of him. It also creates a strategy for cars to gain laps back, loosely resembling the "Lucky dog" rule. However, the cars who get waved around are not allowed to pit until the green flag restarts the race (so they do not get the advantage of getting their lap back AND a free pit stop).


title: Safety car

text: In all NASCAR series, if the caution is out for debris, accident, or inclement weather, the flagman will display the yellow caution flag and the pace car will pull out of the pits and turn on the yellow strobes on top and/or behind the car. When race officials are ready to open pit lane, a green light will come on in the rear window of the safety car. One lap before a green flag, the pace car will shut off its lights to signal drivers to line up double file.


title: Safety car

text: Unlike most series in motorsport, owing to NASCAR's short-track roots, each track usually offers its own safety car, typically from the manufacturer, but in recent years, it has been a local dealer or association of regional dealerships-provided Safety car. Tracks that use Toyota safety cars will use a Toyota Camry Hybrid, while Ford tracks will use a Ford Mustang, while Chevrolet tracks use a Chevrolet Camaro and most Dodge tracks use a Dodge Challenger. If a manufacturer is promoting a new vehicle, they will often use the new car instead of the standard-specification safety car.


title: Safety car

text: For the Truck Series, which races pickup trucks instead of cars, the safety "car" is often a pickup. Tracks affiliated with a local or regional Chevrolet dealership will use a Chevrolet Silverado, while Chrysler dealership-affiliated tracks will use a Ram 1500. Ford-affiliated tracks will often use the F-Series, but Toyota-affiliated tracks are less likely to use the Toyota Tundra, but prefer marketing the Camry Hybrid. However, Ford and Toyota manufacturer sponsored tracks will prefer the Mustang and Camry, respectively, instead of a truck, and occasionally, pickup trucks have been used as pace vehicles for Cup Series and Xfinity races.


title: Safety car

text: Since NASCAR does not allow speedometers or electronic speed limiting devices, the pace car circles the track at pit road speed during the warm-up laps. This allows each driver to note the RPM at which pit road speed is maintained. Drivers exceeding that speed on pit road will be penalized, typically a "drive-through" or "stop and go" penalty, costing them valuable track position.


title: Safety car

text: Since mid-2004, NASCAR official Brett Bodine has driven the vehicle during official race functions during Cup Series races. Other famous NASCAR pace car drivers include Robert "Buster" Auton and Elmo Langley.


title: Safety car

text: At many races, NASCAR has an honorary pace car driver that actually drives a car during the parade laps. Depending on the driver's skill, some drivers are allowed to pace the field right up to the dropping of the green flag. Some famous drivers have been Jay Leno, Richard Hammond, Luke Wilson, Rob Gronkowski, Guy Fieri and many others.


title: Safety car

text: The beneficiary rule (informally known as the "lucky dog" rule) states once the safety car is deployed, the first car not on the lead lap will regain a lap. The Beneficiary will regain his lap once pit road opens. Bodine will signal that car to pass him through radio contact between NASCAR and that team. The free pass car must pit with the lapped cars.


title: Safety car

text: In 2009, NASCAR introduced a new "Double-file restart" rule that lines the field two cars on each row on every restart, similar to the start of the race, instead of lead-lap cars on the outside and lapped cars on the inside. Also, the "wave-around" rule, similar to what is enforced in racing series sanctioned by IndyCar, was adopted to ensure the first car on the restart is the leader, and ensure there are no lapped cars ahead of the leader.


title: Safety car

text: Before the start of the final segment of the Sprint Cup Series' Sprint Unlimited exhibition race at Daytona, the Chevrolet SS pace car caught fire and stopped off the track, delaying the restart. The fire was believed to have started in a trunk-mounted battery pack powering the lights.


title: Safety car

text: During a safety car situation on Lap 160 of the 2012 Daytona 500, Earnhardt Ganassi Racing driver Juan Pablo Montoya's car had a suspension part failure, and it lost control on turn 3, sharply veering into a safety truck and jet dryer trailer and causing a giant fireball. Sparks were seen emanating from Montoya's car right before its hard collision with the jet dryer trailer and left driver's side of the truck. Montoya was treated at the infield care center and released unhurt. The driver of the Chevrolet Silverado Crew Cab, Duane Barnes, was taken to a local hospital for observation and was resting comfortably. He was an employee at Michigan International Speedway, a sister track of Daytona. The tracks often share jet dryer equipment on race weekends to help in case of rain such as the case on Sunday, the original scheduled start time of the race. The entire incident took about two hours to clean up before the last 40 (later extended to 42 due to a Green-white-checkered finish) laps were able to be completed.


title: Safety car

text: NASCAR subsequently added the use of the second safety car (used during race start situations) to protect the last jet dryer in other safety car situations.


title: Safety car

text: The 2011 6 Hours of Castellet got off to a controversial start when the pace car did not return to the pits when the green lights came on. The front running LMPs slowed down but some of the GT cars could not react fast enough, resulting in collisions and heavy damage to all three GTE Pro class Porsches which caused them to retire. The GTE Am class IMSA Performance Matmut Porsche and GTE Pro JOTA Aston Martin were also caught up in the carnage.


title: Safety car

text: An accident occurred during the 2009 FIA WTCC Race of France in Pau, France. A succession of first-lap accidents caused the safety car to be placed on standby, with yellow flags waving on the start-finish section of the track. The safety car driver - a local politician - then proceeded to drive onto the track at slow speed, without official approval, moving across the pit exit line immediately after exiting the pits, instead of confining to the inside of it until the line ended. Race leader Franz Engstler came through the kink on the start-finish straight and was unable to avoid hitting the side of the pace car. Engstler commented "I saw the safety car coming out from the right and realized that I had no chance to brake... I really do not understand why he was going out of the pits". After this incident, the Portuguese Bruno Correia was appointed as the official safety car driver.


title: Safety car

text: A safety car caused a crash during the 2008 Dutch Supercar Challenge race at Spa Francorchamps. The Seat Leon was released too late, allowing the leading Marcos LM600 to pass while erroneously identifying the Audi TT DTM in 2nd and Mosler MT900R GT3 in 3rd as 'the leading pack.' Race officials immediately realized their mistake, and the safety car was instructed to slow down and let the entire field pass.


title: Safety car

text: As the safety car was exiting turn 11, an approaching Lamborghini Gallardo GT3 drastically reduced its speed in response to the unusually slow safety car. However, a BMW a few seconds behind came around the blind turn at speed, colliding with the Gallardo and safety car. The collision destroyed the Gallardo and sent the BMW into a number of rolls. The safety car was sent off the track into the Armco safety barrier at great speed. In the chaos, a Marcos LM600 coming around turn 11 locked up its brakes and spun into the wet grass on the inside of the track. Sliding back onto the track, it was hit from the side by a BMW Z3. Furthermore, two E46 BMW M3 GTRs were damaged: one on the outside line hit the rear of the Marcos, and the other, on the inside line, slightly damaged its front right. The second M3 continued around the track, while the first slid into the grass before turn 12. The race was stopped, and there were no serious injuries to any of the drivers.


title: Safety car

text: On lap 57, ARCA driver Joe Cooksey ran into the back of the Pontiac Grand Prix pace car driven by Jack Wallace totaling the pace car, to quote Cooksey: "It might be the first time in history the pace car has been wiped out."


title: Safety car

text: Before the start of the race, a drunken fan stole the pace car and drove a lap around Talladega Superspeedway. Local police quickly pursued the fan around the track, setting up a roadblock at the exit of Turn 4 that led to his arrest.


title: Safety car

text: The pace car of the 1971 Indianapolis 500, an orange Dodge Challenger driven by local auto dealer Eldon Palmer, crashed at the start of the race. As Palmer drove the car off into the pit lane to let the race cars begin the race, he lost control of the car and crashed into a photographer stand. There were no fatalities, and the number of people reported injured has ranged from 18 to 29.


title: BMW 4 Series (G22)

text: The second generation of the BMW 4 Series consists of the BMW G22 (coupé version) along with the BMW G23 (convertible version) and BMW G26 (saloon version, marketed as the Gran Coupé) compact executive cars. The G22 4 Series was launched in June 2020 and succeeds the F32 4 Series.


title: BMW 4 Series (G22)

text: The G22 will be produced alongside - and shares many features with - the G20 3 Series. As with the G20 3 Series range, the G22/G23/G26 will be powered by turbocharged petrol and diesel engines. Unlike its predecessor, the new 4 Series has a significant departure in design from the 3 Series in order to distinguish between the two models and to move the 4 Series upscale. The most notable of the design changes is the large kidney grille at the front which was inspired by the 1930s BMW 328.


title: BMW 4 Series (G22)

text: The G22 4 Series was unveiled in concept form as the BMW Concept 4, at the 2019 Frankfurt Motor Show and previewing the next generation of the 4 Series. The most notable design feature is the large vertical kidney grille which is inspired by the BMW 328 and 3.0 CSi respectively. The grille has a 3D pattern design to give it a more pronounced look. Other notable design features of the concept were a pronounced duck-tail spoiler at the rear, thin wing mirrors made from a single piece of aluminium and open headlamps, which have no covering over their 3D lighting elements and are instead embedded into the body of the car.


title: BMW 4 Series (G22)

text: On 26 May 2020, BMW announced that the G22 4 Series would be unveiled online in June 2020 by posting a teaser image of the range-topping M440i model. More than 80% of the design cues from the Concept 4 were carried over to the production version including the large kidney grille which now has mesh inserts and is flanked with two slim LED headlamps and two large air intakes (exclusive for the M440i). The rear features wrap around tail lamps and a lip spoiler which is exclusive for the M Sport models. The silhouette of the car is similar to the 8 Series with a tapering roof line. The rear bumper comes with a diffuser on the M Sport models with the M440i having dual exhaust tips. The production version is claimed to have a drag area as low as 0.25 x 2.19 m for the Coupé. On the online unveiling, BMW announced that the worldwide launch of the G22 4 Series would be held in October of the same year.


title: BMW 4 Series (G22)

text: At the end of September, BMW unveiled the convertible version of the new 4 Series (G23), with the same technology and engines as the coupe. It has a canvas roof, unlike the two predecessors which had a retractable hardtop.


title: BMW 4 Series (G22)

text: The launch models consist of the diesel engine 420d, 430d and M440d, the petrol engine 420i M Sport and 430i and the mild hybrid M440i xDrive. The 420i M Sport and 430i feature the 2.0-litre BMW B48 inline-4 engine; rated at and of torque for the 420i M Sport, and and of torque for the 430i. The M440i model is powered by the 3.0-litre turbocharged BMW B58 Inline-6 engine rated at and of torque equipped with a 48-volt electric motor rated at . The 420d is powered by the 2.0-litre turbo-diesel BMW B47 Inline-4 engine rated at while the 430d and M440d are equipped with the 3.0-litre turbo-diesel BMW B57 Inline-6 engine rated at for the 430d and for the 440d. The M440d, like the M440i, is also equipped with a mild hybrid system. The hybrid system features a belt-fed starter generator to recoup energy under braking. This power can be supplied to the car’s 12V electrical system or deployed to assist the combustion engine to help reduce emissions and boost fuel economy.


title: BMW 4 Series (G22)

text: A previously unavailable combination of the 430i with xDrive in their Gran Coupé body will be available as a MY23 version becoming the first 2023 model other than their "iX" electrified SUV. Popular options like a Harman Kardon stereo upgrade, heads-up display and LASER headlights are all available. Orders accepted beginning March according to BMW of NA publications.


title: BMW 4 Series (G22)

text: The only available gearbox is an 8-speed automatic transmission. The M Sport models come with a modified gearbox which features faster shifts and a new "Sprint" driving mode. The 430i, 420d, 430d and M440d come standard with rear-wheel-drive but can be configured with all-wheel-drive. The M440i comes with all wheel drive only. The G22 4 series has a wider track than its predecessor and has 50/50 weight distribution.


title: BMW 4 Series (G22)

text: The 420i can accelerate from 0– in 7.5 seconds, the 430i can accelerate from 0– in 5.5 seconds (5.3 seconds for the xDrive version) while the M440i can accelerate from 0– in 4.3 seconds. All models have an electronically limited top speed of .


title: BMW 4 Series (G22)

text: The 4 Series comes with various exterior packages, such as the M Sport package which adds high gloss exterior trim pieces, a carbon fibre detailing pack which replaces the high gloss trim with carbon fibre and an M Sport Pro package which adds more high gloss trim pieces and 19 inch wheels, unique interior trim and exterior colours. The 4 Series comes standard with the M Sport suspension but buyers can also have the M Adaptive suspension as an option which tweaks steering, damping, and accelerator response. Laser headlamps are also optional aside from the adaptive LED headlamps with hexagonal lighting technology.


title: BMW 4 Series (G22)

text: Most of the interior is carried over from the G20 3 Series upholstered in SensaTec faux leather with front sports seat being standard. The interior is offered in five colours with full leather upholstery being optional. The rear seats fold down to provide a total boot capacity of . The iDrive 7.0 system is standard and features an 8.8-inch screen on the centre console along with a 5.1-inch screen in the instrument cluster. A 10.3 inch screen for the infotainment system along with a 12.3 inch screen for the instrument cluster are optional. The iDrive 7.0 has over-the-air updates for the navigational maps and operating system, and features a voice-controlled digital assistant. The 4 Series comes standard with the BMW navigation, the next-generation BMW head-up display, which has a 70 percent larger projection surface, and 3D environment visualization within the digital instrument cluster. Apple Car Play and Android Auto are also standard interior amenities. A Driving Assistance Professional package is optional, which adds adaptive cruise control with stop and go, lane-keep assist with side collision avoidance, and rear automatic emergency braking.


title: BMW 4 Series (G22)

text: 420-430 models with the M Sport trim and M440 models can be fitted with M Performance Parts. These include a splitter, canards, a lip spoiler, larger wheels and side skirts.


title: Valence bond theory

text: In chemistry, valence bond (VB) theory is one of the two basic theories, along with molecular orbital (MO) theory, that were developed to use the methods of quantum mechanics to explain chemical bonding. It focuses on how the atomic orbitals of the dissociated atoms combine to give individual chemical bonds when a molecule is formed. In contrast, molecular orbital theory has orbitals that cover the whole molecule.


title: Valence bond theory

text: Lothar Meyer in his 1864 book, "Die modernen Theorien der Chemie", contained an early version of the periodic table containing 28 elements, classified elements into six families by their valence—for the first time, elements had been grouped according to their valence. Works on organizing the elements by atomic weight, until then had been stymied by the widespread use of equivalent weights for the elements, rather than atomic weights.


title: Valence bond theory

text: In 1916, G. N. Lewis proposed that a chemical bond forms by the interaction of two shared bonding electrons, with the representation of molecules as Lewis structures. The chemist Charles Rugeley Bury suggested in 1921 that eight and eighteen electrons in a shell form stable configurations. Bury proposed that the electron configurations in transitional elements depended upon the valence electrons in their outer shell. In 1916, Kossel put forth his theory of the ionic chemical bond (octet rule), also independently advanced in the same year by Gilbert N. Lewis. Walther Kossel put forward a theory similar to Lewis' only his model assumed complete transfers of electrons between atoms, and was thus a model of ionic bonding. Both Lewis and Kossel structured their bonding models on that of Abegg's rule (1904).


title: Valence bond theory

text: Although there is no mathematical formula either in chemistry or quantum mechanics for the arrangement of electrons in the atom, the hydrogen atom can be described by the Schrödinger equation and the Matrix Mechanics equation both derived in 1925. However, for hydrogen alone, in 1927 the Heitler–London theory was formulated which for the first time enabled the calculation of bonding properties of the hydrogen molecule H based on quantum mechanical considerations. Specifically, Walter Heitler determined how to use Schrödinger's wave equation (1926) to show how two hydrogen atom wavefunctions join together, with plus, minus, and exchange terms, to form a covalent bond. He then called up his associate Fritz London and they worked out the details of the theory over the course of the night. Later, Linus Pauling used the pair bonding ideas of Lewis together with Heitler–London theory to develop two other key concepts in VB theory: resonance (1928) and orbital hybridization (1930). According to Charles Coulson, author of the noted 1952 book "Valence", this period marks the start of "modern valence bond theory", as contrasted with older valence bond theories, which are essentially electronic theories of valence couched in pre-wave-mechanical terms.


title: Valence bond theory

text: Linus Pauling published in 1931 his landmark paper on valence bond theory: "On the Nature of the Chemical Bond". Building on this article, Pauling's 1939 textbook: "On the Nature of the Chemical Bond" would become what some have called the bible of modern chemistry. This book helped experimental chemists to understand the impact of quantum theory on chemistry. However, the later edition in 1959 failed to adequately address the problems that appeared to be better understood by molecular orbital theory. The impact of valence theory declined during the 1960s and 1970s as molecular orbital theory grew in usefulness as it was implemented in large digital computer programs. Since the 1980s, the more difficult problems, of implementing valence bond theory into computer programs, have been solved largely, and valence bond theory has seen a resurgence.


title: Valence bond theory

text: According to this theory a covalent bond is formed between two atoms by the overlap of "half filled valence" atomic orbitals of each atom containing one unpaired electron. A valence bond structure is similar to a Lewis structure, but where a single Lewis structure cannot be written, several valence bond structures are used. Each of these VB structures represents a specific Lewis structure. This combination of valence bond structures is the main point of resonance theory. Valence bond theory considers that the overlapping atomic orbitals of the participating atoms form a chemical bond. Because of the overlapping, it is most probable that electrons should be in the bond region. Valence bond theory views bonds as weakly coupled orbitals (small overlap). Valence bond theory is typically easier to employ in ground state molecules. The core orbitals and electrons remain essentially unchanged during the formation of bonds.


title: Valence bond theory

text: The overlapping atomic orbitals can differ. The two types of overlapping orbitals are sigma and pi. Sigma bonds occur when the orbitals of two shared electrons overlap head-to-head. Pi bonds occur when two orbitals overlap when they are parallel. For example, a bond between two "s"-orbital electrons is a sigma bond, because two spheres are always coaxial. In terms of bond order, single bonds have one sigma bond, double bonds consist of one sigma bond and one pi bond, and triple bonds contain one sigma bond and two pi bonds. However, the atomic orbitals for bonding may be hybrids. Often, the bonding atomic orbitals have a character of several possible types of orbitals. The methods to get an atomic orbital with the proper character for the bonding is called hybridization.


title: Valence bond theory

text: Modern valence bond theory now complements molecular orbital theory, which does not adhere to the valence bond idea that electron pairs are localized between two specific atoms in a molecule but that they are distributed in sets of molecular orbitals which can extend over the entire molecule. Molecular orbital theory can predict magnetic and ionization properties in a straightforward manner, while valence bond theory gives similar results but is more complicated. Modern valence bond theory views aromatic properties of molecules as due to spin coupling of the orbitals. This is essentially still the old idea of resonance between Friedrich August Kekulé von Stradonitz and James Dewar structures. In contrast, molecular orbital theory views aromaticity as delocalization of the -electrons. Valence bond treatments are restricted to relatively small molecules, largely due to the lack of orthogonality between valence bond orbitals and between valence bond structures, while molecular orbitals are orthogonal. On the other hand, valence bond theory provides a much more accurate picture of the reorganization of electronic charge that takes place when bonds are broken and formed during the course of a chemical reaction. In particular, valence bond theory correctly predicts the dissociation of homonuclear diatomic molecules into separate atoms, while simple molecular orbital theory predicts dissociation into a mixture of atoms and ions. For example, the molecular orbital function for dihydrogen is an equal mixture of the covalent and ionic valence bond structures and so predicts incorrectly that the molecule would dissociate into an equal mixture of hydrogen atoms and hydrogen positive and negative ions.


title: Valence bond theory

text: Modern valence bond theory replaces the overlapping atomic orbitals by overlapping valence bond orbitals that are expanded over a large number of basis functions, either centered each on one atom to give a classical valence bond picture, or centered on all atoms in the molecule. The resulting energies are more competitive with energies from calculations where electron correlation is introduced based on a Hartree–Fock reference wavefunction. The most recent text is by Shaik and Hiberty.


title: Valence bond theory

text: An important aspect of the valence bond theory is the condition of maximum overlap, which leads to the formation of the strongest possible bonds. This theory is used to explain the covalent bond formation in many molecules.


title: Valence bond theory

text: For example, in the case of the F molecule, the F−F bond is formed by the overlap of "p" orbitals of the two F atoms, each containing an unpaired electron. Since the nature of the overlapping orbitals are different in H and F molecules, the bond strength and bond lengths differ between H and F molecules.


title: Valence bond theory

text: In an HF molecule the covalent bond is formed by the overlap of the 1"s" orbital of H and the 2"p" orbital of F, each containing an unpaired electron. Mutual sharing of electrons between H and F results in a covalent bond in HF.


title: Valence bond theory

text: Using modern classical valence bond theory, Patil and Bhanage have shown that the cation-anion interface of protic ionic liquids possesses charge shift bond character.


title: What Lies Below (film)

text: What Lies Below is a 2020 American horror film written and directed by Braden R. Duemmler and starring Ema Horvath, Mena Suvari, and Trey Tucker.


title: What Lies Below (film)

text: A 16 year-old high school girl, Liberty Wells, who goes by Libby, returns to her family lake house after summer camp. Her mother, Michelle Wells, is a romance novelist. Libby meets her mother's new boyfriend, John, an aquatic geneticist, who gives her a bracelet with symbols for the goddess of fertility. John explains that his work involves trying to help creatures adapt to changing environments. Later that night, Libby goes to the kitchen and she hears loud sexual moaning, and runs back to her bed. John stands in her doorway while Libby pretends to be asleep.


title: What Lies Below (film)

text: The next morning, Michelle and Libby dig up time-capsules in the yard, and have an argument about Libby thinking Michelle doesn't care about her grandparents until Michelle tells Libby she felt unwanted by her father. Libby is bitten by a centipede and John helps her. Michelle falls ill, and reveals that John asked her to marry him and she said yes. Libby learns that John is working with parasites. She starts to menstruate and when John sees the blood, he attempts to clean it up with his shirt, and touches her. While Libby showers, John sneaks into the bathroom to smell her through the curtain. Libby removes the bracelet he gave her to find a red mark on her wrist.


title: What Lies Below (film)

text: Libby asks her friend Marley to come to the house. That night, she sees John walking into the lake, which is emitting red lights. John suddenly appears, completely dry, and tells Libby that he suffers from sleep-walking. The next morning, Michelle starts vomiting and sends Libby into town to get medicine and a pregnancy test. Libby follows a man who looks like John with another woman. She returns to the house and tells Marley that John touched her inappropriately. Michelle says that she is pregnant. Libby is disappointed and Michelle thinks that she is making up lies about John touching her. Libby sees that John has a nictitating membrane and tries to pull Michelle away from John but Michelle slaps Libby. Libby reveals Michelle's age which is forty-two not thirty-five then John leaves. She then investigates the basement and notices symbols on her wrist where the bracelet used to be. She discovers Michelle in a tank attached to an IV, with the same symbols on her wrists and on the walls. Libby hides while John watches Michelle give birth to a dying creature.


title: What Lies Below (film)

text: Libby calls the police and discovers Marley's body in a water tank being devoured by parasites. John attacks Libby as she tries to escape with Michelle, and she wakes up tied up in a basement. Several men who look identical to John appear and start to peel the walls back to reveal many unconscious women in water tanks. John regurgitates a glowing substance and forces Libby to consume it. Libby awakes in a row of water tanks containing other women apparently in pupae. As water fills her tank, she initially bangs on the glass but then smiles when she realizes she can breathe underwater.


title: What Lies Below (film)

text: Cath Clarke of "The Guardian" rated the film with 1 out of 5 stars and wrote: "A perplexing erotic storyline isn't the worst thing about this sci-fi mystery, which is marred by wooden acting and poor judgement." Jack Wilhelmi of "Screen Rant" gave it 3 out of 5, designating a "good" rating, offering praise for Horvath and Suvari, but offered negative critique for the film otherwise, writing: "Everything that has been done, from sinister boyfriends to undersea monsters, lacks potency here partially because it's been done before – and sometimes, done to death – and partially because it just barely misses the mark." On Rotten Tomatoes the film has an approval rating of based on reviews from critics. On Metacritic, the film has a score of 35 out of a 100 by 4 critics, indicating "generally unfavorable reviews".


title: What Lies Below (film)

text: Sara Finkel of "Insider" accused the film of "confusing Netflix viewers" and called it "[a] soapy thriller" and "a shallow mishmash of horror tropes".


title: Integrated Services Digital Network

text: Integrated Services Digital Network (ISDN) is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the digitalised circuits of the public switched telephone network. Work on the standard began in 1980 at Bell Labs and was formally standardized in 1988 in the CCITT "Red Book". By the time the standard was released, newer networking systems with much greater speeds were available, and ISDN saw relatively little uptake in the wider market. One estimate suggests ISDN use peaked at a worldwide total of 25 million subscribers at a time when 1.3 billion analog lines were in use. ISDN has largely been replaced with digital subscriber line (DSL) systems of much higher performance.


title: Integrated Services Digital Network

text: Prior to ISDN, the telephone system consisted of digital links like T1/E1 on the long-distance lines between telephone company offices and analog signals on copper telephone wires to the customers, the "last mile". At the time, the network was viewed as a way to transport voice, with some special services available for data using additional equipment like modems or by providing a T1 on the customer's location. What became ISDN started as an effort to digitize the last mile, originally under the name "Public Switched Digital Capacity" (PSDC). This would allow call routing to be completed in an all-digital system, while also offering a separate data line. The Basic Rate Interface, or BRI, is the standard last-mile connection in the ISDN system, offering two 64 kbit/s "bearer" lines and a single 16 kbit/s "delta" channel for commands and data.


title: Integrated Services Digital Network

text: Although ISDN found a number of niche roles and some wider uptake in specific locales, the system was largely ignored and garnered the industry nickname "innovation subscribers didn't need." It found a use for a time for small-office digital connection, using the voice lines for data at 64 kbit/s, sometimes "bonded" to 128 kbit/s, but the introduction of 56 kbit/s modems undercut its value in many roles. It also found use in videoconference systems, where the direct end-to-end connection was desirable. The H.320 standard was designed around its 64 kbit/s data rate. The underlying ISDN concepts found wider use as a replacement for the T1/E1 lines it was originally intended to extend, roughly doubling the performance of those lines.


title: Integrated Services Digital Network

text: Since its introduction in 1881, the twisted pair copper line has been installed for telephone use worldwide, with well over a billion individual connections installed by 2000. Over the first half of the 20th century, the connection of these lines to form calls was increasingly automated, culminating in the crossbar switches that had largely replaced earlier concepts by the 1950s.


title: Integrated Services Digital Network

text: As telephone use surged in the post-WWII era, the problem of connecting the massive number of lines became an area of significant study. Bell Labs' seminal work on digital encoding of voice led to the use of 64 kbit/s as a standard for voice lines (or 56 kbit/s in some systems). In 1962, Robert Aaron of Bell introduced the T1 system, which allowed a pair of twisted pair lines to carry 1.544 Mbit/s of data over a distance of about one mile. This was used in the Bell network to carry traffic between local switch offices, with 24 voice lines at 64 kbit/s and a separate 8 kbit/s line for signaling commands like connecting or hanging up a call. This could be extended over long distances using repeaters in the lines. T1 used a very simple encoding scheme, alternate mark inversion (AMI), which reached only a few percent of the theoretical capacity of the line but was appropriate for 1960s electronics.


title: Integrated Services Digital Network

text: By the late 1970s, T1 lines and their faster counterparts, along with all-digital switching systems, had replaced the earlier analog systems for most of the western world, leaving only the customer's equipment and their local end office using analog systems. Digitizing this "last mile" was increasingly seen as the next problem that needed to be solved. However, these connections now represented over 99% of the total telephony network, as the upstream links had increasingly been aggregated into a smaller number of much higher performance systems, especially after the introduction of fiber optic lines. If the system was to become all-digital, a new standard would be needed that was appropriate for the existing customer lines, which might be miles long and of widely varying quality.


title: Integrated Services Digital Network

text: Around 1978, Ralph Wyndrum, Barry Bossick and Joe Lechleider of Bell Labs began one such effort to develop a last-mile solution. They studied a number of derivatives of the T1's AMI concept and concluded that a customer-side line could reliably carry about 160 kbit/s of data over a distance of . That would be enough to carry two voice-quality lines at 64 kbit/s as well as a separate 16 kbit/s line for data. At the time, modems were normally 300 bps and 1200 bit/s would not become common until the early 1980s and the 2400 bit/s standard would not be completed until 1984. In this market, 16 kbit/s represented a significant advance in performance in addition to being a separate channel and thus allowing voice and data at the same time.


title: Integrated Services Digital Network

text: A key problem was that the customer might only have a single twisted pair line to the location of the handset, so the solution used in T1 with separate upstream and downstream connections was not universally available. With analog connections, the solution was to use echo cancellation, but at the much higher bandwidth of the new concept, this would not be so simple. A debate broke out between teams worldwide about the best solution to this problem; some promoted newer versions of echo cancellation, while others preferred the "ping pong" concept where the direction of data would rapidly switch the line from send to receive at such a high rate it would not be noticeable to the user. John Cioffi had recently demonstrated echo cancellation would work at these speeds, and further suggested that they should consider moving directly to 1.5 Mbit/s performance using this concept. The suggestion was literally laughed off the table (His boss told him to "sit down and shut up") but the echo cancellation concept was taken up by Joe Lechleider eventually came to win the debate.


title: Integrated Services Digital Network

text: Meanwhile, the debate over the encoding scheme itself was also ongoing. As the new standard was to be international, this was even more contentious as several regional digital standards had emerged in the 1960s and 70s and merging them was not going to be easy. To further confuse issues, in 1984 the Bell System was broken up and the US center for development moved to the American National Standards Institute (ANSI) T1D1.3 committee. Thomas Starr of the newly formed Ameritech led this effort and eventually convinced the ANSI group to select the 2B1Q standard proposed by Peter Adams of British Telecom. This standard used an 80 kHz base frequency and encoded two bits per baud to produce the 160 kbit/s base rate. Ultimately Japan selected a different standard, and Germany selected one with three levels instead of four, but all of these could interchange with the ANSI standard.


title: Integrated Services Digital Network

text: From an economic perspective, the European Commission sought to liberalize and regulate ISDN across the European Economic Community. The Council of the European Communities adopted Council Recommendation 86/659/EEC in December 1986 for its coordinated introduction within the framework of CEPT. ETSI (the European Telecommunications Standards Institute) was created by CEPT in 1988 and would develop the framework.


title: Integrated Services Digital Network

text: With ISDN allowing digital-quality voice, two separate lines and all-the-time data, the telephony world was convinced there would be high customer demand for such systems in both the home and office. This proved not to be the case. During the lengthy standardization process, new concepts rendered the system largely superfluous. In the office, multi-line digital switches like the Meridian Norstar took over telephone lines while local area networks like Ethernet provided performance around 10 Mbit/s which had become the baseline for inter-computer connections in offices. ISDN offered no real advantages in the voice role and was far from competitive in data. Additionally, modems had continued improving, introducing 9600 bit/s systems in the late 1980s and 14.4 kbit/s in 1991, which significantly eroded ISDN's value proposition for the home customer.


title: Integrated Services Digital Network

text: Meanwhile, Lechleider had proposed using ISDN's echo cancellation and 2B1Q encoding on existing T1 connections, allowing the distance between repeaters to be doubled to about . Another standards war broke out, but in 1991 Lechleider's 1.6 Mbit/s "High-Speed Digital Subscriber Line" eventually won this process as well, after Starr drove it through the ANSI T1E1.4 group. A similar standard emerged in Europe to replace their E1 lines, increasing the sampling range from 80 to 100 kHz to allow 2.048 Mbit/s. By the mid-1990s, these Primary Rate Interface (PRI) lines had largely replaced T1 and E1 between telephone company offices.


title: Integrated Services Digital Network

text: Lechleider also believed this higher-speed standard would be much more attractive to customers than ISDN had proven. Unfortunately, at these speeds, the systems suffered from a type of crosstalk known as "NEXT", for "near-end crosstalk". This made longer connections on customer lines difficult. Lechleider noted that NEXT only occurred when similar frequencies were being used, and could be diminished if one of the directions used a different carrier rate, but doing so would reduce the potential bandwidth of that channel. Lechleider suggested that most consumer use would be asymmetric anyway, and that providing a high-speed channel towards the user and a lower speed return would be suitable for many uses.


title: Integrated Services Digital Network

text: This work in the early 1990s eventually led to the ADSL concept, which emerged in 1995. An early supporter of the concept was Alcatel, who jumped on ADSL while many other companies were still devoted to ISDN. Krish Prabu stated that "Alcatel will have to invest one billion dollars in ADSL before it makes a profit, but it is worth it." They introduced the first DSL Access Multiplexers (DSLAM), the large multi-modem systems used at the telephony offices, and later introduced customer ADSL modems under the Thomson brand. Alcatel remained the primary vendor of ADSL systems for well over a decade.


title: Integrated Services Digital Network

text: ADSL quickly replaced ISDN as the customer-facing solution for last-mile connectivity. ISDN has largely disappeared on the customer side, remaining in use only in niche roles like dedicated teleconferencing systems and similar legacy systems.


title: Integrated Services Digital Network

text: "Integrated services" refers to ISDN's ability to deliver at minimum two simultaneous connections, in any combination of data, voice, video, and fax, over a single line. Multiple devices can be attached to the line, and used as needed. That means an ISDN line can take care of what were expected to be most people's complete communications needs (apart from broadband Internet access and entertainment television) at a much higher transmission rate, without forcing the purchase of multiple analog phone lines. It also refers to integrated switching and transmission in that telephone switching and carrier wave transmission are integrated rather than separate as in earlier technology.


title: Integrated Services Digital Network

text: In ISDN, there are two types of channels, "B" (for "bearer") and "D" (for "data"). "B channels" are used for data (which may include voice), and "D channels" are intended for signaling and control (but can also be used for data).


title: Integrated Services Digital Network

text: There are two ISDN implementations. Basic Rate Interface (BRI), also called basic rate access (BRA) — consists of two B channels, each with bandwidth of 64 kbit/s, and one D channel with a bandwidth of 16 kbit/s. Together these three channels can be designated as 2B+D. Primary Rate Interface (PRI), also called primary rate access (PRA) in Europe — contains a greater number of B channels and a D channel with a bandwidth of 64 kbit/s. The number of B channels for PRI varies according to the nation: in North America and Japan it is 23B+1D, with an aggregate bit rate of 1.544 Mbit/s (T1); in Europe, India and Australia it is 30B+2D, with an aggregate bit rate of 2.048 Mbit/s (E1). Broadband Integrated Services Digital Network (BISDN) is another ISDN implementation and it is able to manage different types of services at the same time. It is primarily used within network backbones and employs ATM.


title: Integrated Services Digital Network

text: Another alternative ISDN configuration can be used in which the B channels of an ISDN BRI line are bonded to provide a total duplex bandwidth of 128 kbit/s. This precludes use of the line for voice calls while the internet connection is in use. The B channels of several BRIs can be bonded, a typical use is a 384K videoconferencing channel.


title: Integrated Services Digital Network

text: Using bipolar with eight-zero substitution encoding technique, call data is transmitted over the data (B) channels, with the signaling (D) channels used for call setup and management. Once a call is set up, there is a simple 64 kbit/s synchronous bidirectional data channel (actually implemented as two simplex channels, one in each direction) between the end parties, lasting until the call is terminated. There can be as many calls as there are bearer channels, to the same or different end-points. Bearer channels may also be multiplexed into what may be considered single, higher-bandwidth channels via a process called B channel BONDING, or via use of Multi-Link PPP "bundling" or by using an H0, H11, or H12 channel on a PRI.


title: Integrated Services Digital Network

text: The D channel can also be used for sending and receiving X.25 data packets, and connection to X.25 packet network, this is specified in X.31. In practice, X.31 was only commercially implemented in the UK, France, Japan and Germany.


title: Integrated Services Digital Network

text: A set of "reference points" are defined in the ISDN standard to refer to certain points between the telco and the end user ISDN equipment.


title: Integrated Services Digital Network

text: Most NT-1 devices can perform the functions of the NT2 as well, and so the S and T reference points are generally collapsed into the S/T reference point.


title: Integrated Services Digital Network

text: In North America, the NT1 device is considered customer premises equipment (CPE) and must be maintained by the customer, thus, the U interface is provided to the customer. In other locations, the NT1 device is maintained by the telco, and the S/T interface is provided to the customer. In India, service providers provide U interface and an NT1 may be supplied by Service provider as part of service offering.


title: Integrated Services Digital Network

text: The entry level interface to ISDN is the Basic Rate Interface (BRI), a 128 kbit/s service delivered over a pair of standard telephone copper wires. The 144 kbit/s overall payload rate is divided into two 64 kbit/s bearer channels ('B' channels) and one 16 kbit/s signaling channel ('D' channel or data channel). This is sometimes referred to as 2B+D.


title: Integrated Services Digital Network

text: BRI-ISDN is very popular in Europe but is much less common in North America. It is also common in Japan — where it is known as INS64.


title: Integrated Services Digital Network

text: The other ISDN access available is the Primary Rate Interface (PRI), which is carried over T-carrier (T1) with 24 time slots (channels) in North America, and over E-carrier (E1) with 32 channels in most other countries. Each channel provides transmission at a 64 kbit/s data rate.


title: Integrated Services Digital Network

text: With the E1 carrier, the available channels are divided into 30 bearer ("B") channels, one data ("D") channel, and one timing and alarm channel. This scheme is often referred to as 30B+2D.


title: Integrated Services Digital Network

text: In North America, PRI service is delivered via T1 carriers with only one data channel, often referred to as 23B+D, and a total data rate of 1544 kbit/s. Non-Facility Associated Signalling (NFAS) allows two or more PRI circuits to be controlled by a single D channel, which is sometimes called "23B+D + n*24B". D-channel backup allows for a second D channel in case the primary fails. NFAS is commonly used on a Digital Signal 3 (DS3/T3).


title: Integrated Services Digital Network

text: PRI-ISDN is popular throughout the world, especially for connecting private branch exchanges to the public switched telephone network (PSTN).


title: Integrated Services Digital Network

text: Even though many network professionals use the term "ISDN" to refer to the lower-bandwidth BRI circuit, in North America BRI is relatively uncommon whilst PRI circuits serving PBXs are commonplace.


title: Integrated Services Digital Network

text: The bearer channel (B) is a standard 64 kbit/s voice channel of 8 bits sampled at 8 kHz with G.711 encoding. B-channels can also be used to carry data, since they are nothing more than digital channels.


title: Integrated Services Digital Network

text: Most B channels can carry a 64kbit/s signal, but some were limited to 56K because they traveled over RBS lines. This was commonplace in the 20th century, but has since become less so.


title: Integrated Services Digital Network

text: X.25 can be carried over the B or D channels of a BRI line, and over the B channels of a PRI line. X.25 over the D channel is used at many point-of-sale (credit card) terminals because it eliminates the modem setup, and because it connects to the central system over a B channel, thereby eliminating the need for modems and making much better use of the central system's telephone lines.


title: Integrated Services Digital Network

text: X.25 was also part of an ISDN protocol called "Always On/Dynamic ISDN", or AO/DI. This allowed a user to have a constant multi-link PPP connection to the internet over X.25 on the D channel, and brought up one or two B channels as needed.


title: Integrated Services Digital Network

text: In theory, Frame Relay can operate over the D channel of BRIs and PRIs, but it is seldom, if ever, used.


title: Integrated Services Digital Network

text: ISDN is a core technology in the telephone industry. A telephone network can be thought of as a collection of wires strung between switching systems. The common electrical specification for the signals on these wires is T1 or E1. Between telephone company switches, the signaling is performed via SS7. Normally, a PBX is connected via a T1 with robbed bit signaling to indicate on-hook or off-hook conditions and MF and DTMF tones to encode the destination number. ISDN is much better because messages can be sent much more quickly than by trying to encode numbers as long (100 ms per digit) tone sequences. This results in faster call setup times. Also, a greater number of features are available and fraud is reduced.


title: Integrated Services Digital Network

text: In common use, ISDN is often limited to usage to Q.931 and related protocols, which are a set of signaling protocols establishing and breaking circuit-switched connections, and for advanced calling features for the user. Another usage was the deployment of videoconference systems, where a direct end-to-end connection is desirable. ISDN uses the H.320 standard for audio coding and video coding.


title: Integrated Services Digital Network

text: ISDN is also used as a smart-network technology intended to add new services to the public switched telephone network (PSTN) by giving users direct access to end-to-end circuit-switched digital services and as a backup or failsafe circuit solution for critical use data circuits.


title: Integrated Services Digital Network

text: One of ISDNs successful use-cases was in the videoconference field, where even small improvements in data rates are useful, but more importantly, its direct end-to-end connection offers lower latency and better reliability than packet-switched networks of the 1990s. The H.320 standard for audio coding and video coding was designed with ISDN in mind, and more specifically its 64 kbit/s basic data rate. including audio codecs such as G.711 (PCM) and G.728 (CELP), and discrete cosine transform (DCT) video codecs such as H.261 and H.263.


title: Integrated Services Digital Network

text: ISDN is used heavily by the broadcast industry as a reliable way of switching low-latency, high-quality, long-distance audio circuits. In conjunction with an appropriate codec using MPEG or various manufacturers' proprietary algorithms, an ISDN BRI can be used to send stereo bi-directional audio coded at 128 kbit/s with 20 Hz – 20 kHz audio bandwidth, although commonly the G.722 algorithm is used with a single 64 kbit/s B channel to send much lower latency mono audio at the expense of audio quality. Where very high quality audio is required multiple ISDN BRIs can be used in parallel to provide a higher bandwidth circuit switched connection. BBC Radio 3 commonly makes use of three ISDN BRIs to carry 320 kbit/s audio stream for live outside broadcasts. ISDN BRI services are used to link remote studios, sports grounds and outside broadcasts into the main broadcast studio. ISDN via satellite is used by field reporters around the world. It is also common to use ISDN for the return audio links to remote satellite broadcast vehicles.


title: Integrated Services Digital Network

text: In many countries, such as the UK and Australia, ISDN has displaced the older technology of equalised analogue landlines, with these circuits being phased out by telecommunications providers. Use of IP-based streaming codecs such as Comrex ACCESS and ipDTL is becoming more widespread in the broadcast sector, using broadband internet to connect remote studios.


title: Integrated Services Digital Network

text: Providing a backup line for business's inter-office and internet connectivity was a popular use of the technology.


title: Integrated Services Digital Network

text: A study of the German Department of Science shows the following spread of ISDN-channels per 1,000 inhabitants in 2005:


title: Integrated Services Digital Network

text: Telstra provides the business customer with the ISDN services. There are five types of ISDN services which are ISDN2, ISDN2 Enhanced, ISDN10, ISDN20 and ISDN30. Telstra changed the minimum monthly charge for voice and data calls. In general, there are two group of ISDN service types; The Basic Rate services – ISDN 2 or ISDN 2 Enhanced. Another group of types are the Primary Rate services, ISDN 10/20/30. Telstra announced that the new sales of ISDN product would be unavailable as of 31 January 2018. The final exit date of ISDN service and migration to the new service would be confirmed by 2022.


title: Integrated Services Digital Network

text: France Telecom offers ISDN services under their product name Numeris (2 B+D), of which a professional Duo and home Itoo version is available. ISDN is generally known as RNIS in France and has widespread availability. The introduction of ADSL is reducing ISDN use for data transfer and Internet access, although it is still common in more rural and outlying areas, and for applications such as business voice and point-of-sale terminals.


title: Integrated Services Digital Network

text: In Germany, ISDN was very popular with an installed base of 25 million channels (29% of all subscriber lines in Germany as of 2003 and 20% of all ISDN channels worldwide). Due to the success of ISDN, the number of installed analog lines was decreasing. Deutsche Telekom (DTAG) offered both BRI and PRI. Competing phone companies often offered ISDN only and no analog lines. However, these operators generally offered free hardware that also allows the use of POTS equipment, such as NTBAs ("": small devices that bridge the two-wire UK0 line to the four-wire S0 bus) with integrated terminal adapters. Because of the widespread availability of ADSL services, ISDN was primarily used for voice and fax traffic.


title: Integrated Services Digital Network

text: Until 2007 ISDN (BRI) and ADSL/VDSL were often bundled on the same line, mainly because the combination of DSL with an analog line had no cost advantage over a combined ISDN-DSL line. This practice turned into an issue for the operators when vendors of ISDN technology stopped manufacturing it and spare parts became hard to come by. Since then phone companies started introducing cheaper xDSL-only products using VoIP for telephony, also in an effort to reduce their costs by operating separate data & voice networks.


title: Integrated Services Digital Network

text: Since approximately 2010, most German operators have offered more and more VoIP on top of DSL lines and ceased offering ISDN lines. New ISDN lines have been no longer available in Germany since 2018, existing ISDN lines were phased out from 2016 onwards and existing customers were encouraged to move to DSL-based VoIP products.


title: Integrated Services Digital Network

text: Deutsche Telekom intended to phase-out by 2018 but postponed the date to 2020, other providers like Vodafone estimate to have their phase-out completed by 2022.


title: Integrated Services Digital Network

text: OTE, the incumbent telecommunications operator, offers ISDN BRI (BRA) services in Greece. Following the launch of ADSL in 2003, the importance of ISDN for data transfer began to decrease and is today limited to niche business applications with point-to-point requirements.


title: Integrated Services Digital Network

text: Bharat Sanchar Nigam Limited, Reliance Communications and Bharti Airtel are the largest communication service providers, and offer both ISDN BRI and PRI services across the country. Reliance Communications and Bharti Airtel uses the DLC technology for providing these services. With the introduction of broadband technology, the load on bandwidth is being absorbed by ADSL. ISDN continues to be an important backup network for point-to-point leased line customers such as banks, Eseva Centers, Life Insurance Corporation of India, and SBI ATMs.


title: Integrated Services Digital Network

text: On April 19, 1988, Japanese telecommunications company NTT began offering nationwide ISDN services trademarked INS Net 64, and INS Net 1500, a fruition of NTT's independent research and trial from the 1970s of what it referred to the INS (Information Network System).