6 definitions in this view. Search all 509 terms by name, phrase or topic.
Routing glossary · AI Glossary · About these definitions
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- Transport & aerospaceOBD
On-board diagnostics: a vehicle's built-in monitoring and reporting capabilities. Standardized OBD-II diagnostics monitor emission-related systems and provide information that a compatible scan tool can retrieve, including trouble codes. Access to additional modules, live data and service functions depends on the exact vehicle, tool and software; check the specific task's coverage.
Guide: Car Scan Tools: Choose the Coverage You Actually Need
Reference: California Air Resources Board: OBD-II systems
Link to this term- Computers & specificationsOCR
Optical character recognition: converting pictures of written or printed text into machine-readable characters. Layout, image quality and the writing system affect accuracy, so important extracted text needs checking.
Related coverage: Scanning pen
Link to this term- NetworksOptical fiber
A thin strand of transparent material that guides light carrying information. Fiber type, optical wavelength, transceivers and the link's losses determine the connection it can support.
Link to this term- Historical names & systemsOPX
Off-premises extension: a telephone extension located away from the premises containing its main switching system. Its connection and service arrangement determine how calls reach it.
Related coverage: PBX definition
Link to this term- Rocks & EarthOrthometric height
Height relative to the geoid, measured along the direction of gravity and commonly written H. It provides the basis for many surveyed elevations. The usual conversion is H = h − N, using compatible ellipsoidal height h and geoid height N. Record the vertical datum and model because height references can differ between datasets.
Guide: GPS Surveying: Reference Systems, Field Records, and Quality Checks
Reference: NOAA NGS: orthometric heights, datums and geoid corrections
Link to this term- NetworksOSI model
The Open Systems Interconnection reference model, which organizes communications functions into seven layers. It is useful for describing responsibilities and troubleshooting, while real protocol stacks may cross or combine its conceptual boundaries.
Read the guide: OSI Layers in Practice: Follow a Connection, Find a Fault
Reference: ITU: OSI reference model
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A starting point for understanding
Each entry gives a concise meaning and, where useful, a distinction or practical example. Topic labels identify the context; the same acronym can have several meanings. Historical names remain useful when reading older coverage.
Follow the linked Yenra guides for fuller explanations and the reference links for supporting documentation. Health, technical and regulatory terms describe concepts; individual decisions depend on the applicable evidence, equipment and circumstances.
Collection updated October 13, 2026. Full glossary · AI Glossary