The circuit of a control apparatus or system that carries the electric signals directing the performance of the controller but does not carry the main power current. (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}