A metal raceway of circular cross section with integral or associated couplings, connectors, and fittings approved for the installation of electrical conductors. (NFPA 70, National Electrical Code)
Pinnacle Systems, Inc. (Safety Sensors and Controls for Industrial Machine Guarding Systems), Safety Glossary, Pittsburgh, Pennsylvania, USA 2014. http://www.pinnaclesystems.com/Glossary-B-I.html, (Ergo - Amer) {759}