2T/4T TIG operations

2T is what I used most on my portable inverter for TIG at Breweries. It is the simplest version of a sequencer. One tap gives you pre-flow gas, and initial amperage, and a ramp up to the welding amperage (or pulser). The second tap ramps down to a final amperage and then gives you post-flow gas.
4T does all that 2T does, but also allows you to go between 2 different amperages without using a foot pedal or slider for amperage control.
I have never found a use for it in my work, but I can see it working for repetitive welding in a production environment.