Safety switch key is to prevent from unauthorized user. Program the button function by computer software. Up/down, east/west, south/north can be programmed to interlock or non-interlock, toggle or normal etc. Spare buttons 1-4 can be programed to be normal, toggle, interlock, on/off etc.Start button can be program to be start, normal, toggle function etc. International Buyers - Please Note: a. Misused or abused merchandise will not be accounted as defective. We will reply you ASAP. Our aim is to provide Top Level Customer Service, normally so we will try our best to solve any problem. If you are dissatisfied for any reason, please donot be quick to leave negative/neutral feedback.