This is a speed indicator/encoder wheel, It was made up for a machine at a manufacturing plant. I've been asked to make up another one. The control box has 120 volt power feeding it from the cord on the left,The encoder wire on the right is class 2 wiring. They both attach to the back of the controller in the box. My question is this in violation of art:725.136, The controller is capable of being powered by 24VDC. If this is a violation would I be better to use a 24VDC wall plugin transformer instead of the 120V?