A device designed to open and close a circuit by non-automatic means and to open the circuit automatically on a predetermined overcurrent without injury to itself when properly applied within its rating. (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}