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Communications system
A communications system is the set of components that conveys information from a source to a destination through a channel, following the five-element model Claude Shannon formalized in 1948.
Communications Workers of America
The Communications Workers of America, founded in 1947 as the National Federation of Telephone Workers, is a labor union representing about 700,000 workers in the United States and Canada.
Communications Workers of America v. Beck
Communications Workers of America v. Beck, also known as CWA v. Beck, is a 1988 Supreme Court decision limiting how unions may spend nonmembers' compelled fees.
Communications-based train control
Communications-based train control (CBTC) is an automatic railway signaling system that locates trains by radio rather than track circuits, allowing more trains to run closer together.
Communications-Electronics Research, Development and Engineering Center
The Communications-Electronics Research, Development and Engineering Center (CERDEC) was the U.S. Army's research center for communications, intelligence, and mission command technologies, becoming the C5ISR Center in 2019.
Communications, Electrical and Plumbing Union of Australia
The Communications, Electrical and Plumbing Union, known as the CEPU, is an Australian trade union representing communications, electrical, energy, postal, and plumbing workers, formed by merger in August 1994.
Community choice aggregation
Community choice aggregation (CCA) is a program letting cities and counties become the default electricity supplier for their residents, while the incumbent utility delivers the power and customers can opt out.
Community Energy (company)
Community Energy, Inc. is an American renewable energy company founded in 1999 in Radnor, Pennsylvania, which began selling retail wind power and became a large-scale solar developer.
Community Networks
Community networks are communications networks built, owned, and operated by the people who use them through cooperatives or nonprofits, also a public health term for grassroots organizations cooperating toward a common goal.
Community Notes
Community Notes, originally called Birdwatch, is a crowdsourced fact-checking feature on X (formerly Twitter), shown on posts only when contributors with differing viewpoints rate them helpful.
Community Offshore Wind
Community Offshore Wind was a US offshore wind joint venture of RWE and National Grid Ventures holding lease OCS-A 0539 in the New York Bight, canceled in 2026.
Community Rating System
The Community Rating System (CRS) is a voluntary FEMA program, created in 1990, that rewards communities for floodplain management exceeding minimum requirements with discounts on flood insurance premiums.
Community search
Community search is a graph mining method that, given a graph and query nodes, returns a connected, densely connected subgraph containing them, using models such as k-core and k-truss.
Commutator (electric)
A commutator is a rotating electrical switch of insulated copper segments and carbon brushes mounted on a DC machine's shaft, maintaining unidirectional torque in motors and rectifying AC into DC in generators.
Commuter rail
Commuter rail, also called suburban rail, is regional passenger train service linking suburbs with a central city, with longer trains, fewer stops, and peak-hour schedules.
Compact car
A compact car is a passenger vehicle smaller than a midsize car but larger than a subcompact, defined in the US by an interior volume of 100 to under 110 cubic feet.
Compact disc
The compact disc (CD) is a 120 mm optical disc storing digital audio or data, developed by Philips and Sony, standardized in 1980, and introduced commercially in 1982.
Compact disc bronzing
Compact disc bronzing is disc rot in which a CD's reflective layer corrodes, turning bronze from the edge inward; chiefly affects 1988-1993 PDO (Blackburn, UK) pressings whose lacquer failed against sulfur in paper booklets.
Compact Disc Digital Audio
Compact Disc Digital Audio (CD-DA) is the optical disc format for stereo music on the standard audio CD, defined by Philips and Sony in 1980 and launched in 1982.
Compact executive car
A compact executive car, also called an entry-level luxury car, is a premium-badged sedan or estate below full-size luxury models, dominated by the BMW 3 Series, Mercedes C-Class, and Audi A4.
Compact fluorescent lamp
A compact fluorescent lamp (CFL) is a fluorescent lamp with a bent spiral tube designed to fit household fixtures, invented by Edward Hammer at General Electric in 1976.
Compact inverse-Compton X-ray source
A compact inverse-Compton X-ray source is a laboratory-scale device that makes X-rays by colliding relativistic electrons with laser photons, delivering brilliance between an X-ray tube and a synchrotron.
Compact MPV
A compact MPV, or compact multi-purpose vehicle, is a small family car about 4 to 4.5 meters long, with a raised roofline and flexible seating, pioneered by the 1996 Renault Scénic.
CompacT SelecT
CompacT SelecT is a compact robotic cell-culture workcell developed by The Automation Partnership and unveiled in 2006 as a smaller, more affordable version of the full-size SelecT system for pharmaceutical, biotech, and academic labs.
Compact toroid
A compact toroid (CT), also called a compact torus, is a magnetically confined plasma torus with no center column, covering two configurations, the field-reversed configuration and the spheromak.
Compact transmission line
A compact transmission line is an overhead power line built with reduced phase spacing and shorter insulators, so more power flows through a narrower right-of-way than a conventional design allows.
Compact Video Cassette
Compact Video Cassette (CVC) was an analog videotape format introduced in 1980 by Funai Electric, marketed mainly as Technicolor, that failed against VHS and Betamax.
CompactFlash
CompactFlash, also called a CF card, is a removable memory card format introduced by SanDisk in 1994, widely used in digital cameras until SD cards largely replaced it.
Compaction grouting
Compaction grouting is a ground improvement technique, pioneered in the United States in the 1950s, that densifies loose soil by injecting stiff, low-mobility grout to displace and compact it.
CompactPCI
CompactPCI (cPCI) is an industrial computer standard, ratified by PICMG in 1995, that places the PCI bus on rugged Eurocard mechanics for industrial, telecom, and defense systems.