I have a blue brand inverta TIG 180p.This welder was bought for me over 10 years ago, and has never been used until a few days ago. It came with a basic instruction book with no set up details. It has slope in & out controls which I assume is the amperage at start & finish, does this also control the gas pre flow? and not sure what the 2T and 4T switch does. The more I look at You Tube the more confused I get. Thank's Yetta