"Cold switch," not "cold start." Anyway, per their website: "The latest of the new Models, introduced in early 2004 is the -CS model variations. The Cold Switch Models have added a safety feature of trigger release cutoff from live power to the unit, when not welding." Also: "This system is designed to protect the operator from accidentally striking an arc without the trigger pulled. The solenoid is deactivated when you release the trigger, allowing you to lay the welder down or to avoid arcing out your grounded surfaces without any worries. This feature was manufactured with safety in mind."