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Ring-core fiber
Ring-core fiber is an optical fiber that guides light in a ring-shaped annulus of high refractive index instead of a solid core, built to carry twisted orbital angular momentum modes.
Ringback tone
A ringback tone, also called ringing tone or audible ringing tone, is the sound a caller hears while the called party's telephone is being alerted, generated by the network.
RingCentral
RingCentral is an American provider of cloud-based business communications software, founded in 1999 by Vlad Shmunis and Vlad Vendrow and headquartered in Belmont, California. Its offerings include unified communications, contact center, and video services.
Ringdown
Ringdown is a telephony signaling method in which ringing current alerts an operator or called station without dialing; ringdown circuits connect two endpoints directly, so lifting the handset rings the far end.
Ringedals Dam
Ringedals Dam (Ringedalsdammen) is a concrete gravity dam at the head of Ringedalsvatnet in Skjeggedal, above Tyssedal in Vestland, Norway. Built 1910–1918 for the Tysso I hydroelectric plant, it was Norway's largest dam when completed.
Ringhals nuclear power plant
Ringhals is a Swedish nuclear power plant on the Värö peninsula, about 60 kilometers south of Gothenburg, where two pressurized water reactors produce around 17 TWh per year.
Ringhorne oil field
Ringhorne is an oil field in the Norwegian sector of the North Sea, in the southern Viking Graben, producing since 2003 from a platform and operated by Vår Energi.
Ringing (telephony)
Ringing in telephony is the alerting of a called party to an incoming call, produced by alternating ringing voltage on the line; the word also covers the caller's ringback tone.
Ringing signal
A ringing signal is the high-voltage, low-frequency AC voltage a telephone exchange, PBX, or analog adapter applies to a subscriber line to alert the called party of an incoming call.
Ringtone
A ringtone, also called a mobile phone ringtone, is the sound a phone plays to signal an incoming call; Nokia's tune introduced the musical ringtone in 1994.
Rio Bravo Pipeline
The Rio Bravo Pipeline is a proposed natural gas pipeline system in South Texas, running from the Agua Dulce hub to NextDecade's Rio Grande LNG terminal in Brownsville.
Rio de Janeiro/Galeão International Airport
Rio de Janeiro/Galeão International Airport, also named for Antônio Carlos Jobim, is Brazil's second-largest international hub. Opened in 1952 in Rio de Janeiro, it has been operated by Spain's Aena since 2026.
Rio Grande diversion canals
The Rio Grande diversion canals are irrigation canals in New Mexico and west Texas, belonging to the Middle Rio Grande Conservancy District and the federal Rio Grande Project.
Rio Grande LNG
Rio Grande LNG is a natural gas export facility under construction at the Port of Brownsville, south Texas, developed by NextDecade, with first LNG expected in 2027.
Rio Grande Project
The Rio Grande Project, also called the Rio Grande Reclamation Project, is a US Bureau of Reclamation irrigation and power project on the Rio Grande in New Mexico and west Texas.
Rio Urucu Oil and Gas Field
Rio Urucu is an onshore oil and natural gas field in the Solimões Basin of the Brazilian Amazon, discovered by Petrobras in 1986 in Coari, Amazonas.
Rio–Antirrio Bridge
The Rio–Antirrio Bridge (Γέφυρα Ρίου-Αντιρρίου), officially the Charilaos Trikoupis Bridge, is a cable-stayed road bridge in Greece linking Rio on the Peloponnese with Antirrio, inaugurated in 2004.
Rio–Antirrio Bridge (Γέφυρα Ρίου-Αντιρρίου)
The Rio–Antirrio Bridge (Γέφυρα Ρίου-Αντιρρίου), officially the Charilaos Trikoupis Bridge, is a cable-stayed bridge near Patras, Greece, opened in 2004 to link the Peloponnese with the mainland.
Rio–Niterói Bridge
The Rio–Niterói Bridge (Ponte Rio–Niterói) is a box girder bridge crossing Guanabara Bay, connecting Rio de Janeiro and Niterói. Inaugurated in 1974, it carries the BR-101 highway.
Rio2 Limited
Rio2 Limited is a Canadian mining company headquartered in Vancouver that operates the Fenix Gold Mine in Chile and the Condestable Copper Mine in Peru.
Riot control agent
A riot control agent is a chemical, such as tear gas or pepper spray, that causes short-lived sensory irritation and is used by police for crowd control.
Ripio
Ripio is an Argentine cryptocurrency platform founded in 2013 as BitPagos and rebranded in 2017, providing a retail wallet and exchange, a Visa card, and business-to-business crypto infrastructure.
Ripple (electrical)
Ripple, also called ripple voltage, is the periodic AC voltage superimposed on a power supply's DC output, caused by incomplete suppression of the alternating waveform.
Ripple Labs
Ripple Labs, shortened to Ripple, is an American blockchain and fintech company that builds payments, custody, and stablecoin products and is tied to the XRP Ledger and XRP.
Rippling (company)
Rippling is a San Francisco workforce management software company that unifies HR, payroll, IT, and finance tools, founded in 2016 by former Zenefits executive Parker Conrad and Prasanna Sankar.
Riprap
Riprap, also called shot rock or rock armor, is a layer of large loose stone or concrete blocks placed to protect soil from erosion by water.
Riqueval Tunnel
The Riqueval Tunnel (souterrain de Riqueval), also called the Grand Souterrain, is a 5,670-meter navigable canal tunnel on the Canal de Saint-Quentin in northern France, opened in 1810.
RIS (file format)
RIS is a plain-text bibliographic interchange format introduced in 1988 by Research Information Systems, used behind most journal citation exports and read by reference managers like EndNote, Zotero, and Mendeley.
RISA (software)
RISA is a suite of structural engineering software for the analysis and design of buildings, foundations, and connections, developed in California and part of the Nemetschek Group.
RISAT
RISAT (Radar Imaging Satellite) is a series of Indian Earth observation satellites built by ISRO, beginning with RISAT-2 in 2009, whose radar payloads image the surface at night and through clouds.