It's a short tap of the single button Matt, the short tap (on 4t only i believe) activates secondary current, another tap disables it, and a button hold ramps the current down to end as usual. I believe Esab, Lincoln and a few others have had this on a few models, designed specifically for single button torches. I have to admit, I find using the Lorch secondary current button quite difficult, you have to hold your hand a certain way so you can either move your finger/thumb from one to another, or you have to roll the finger/thumb over onto it. But it's not something I personally need to use in reality - guess I'd get used to it if I used it every day. I never have the problem of accidentally triggering it, though.