Power Supply Question

I just bought a new PC case and the power supply has a slider switch on it with three positions, each lettered as “T,” “A,” and I think “M” (I’m at work, away from the case). What the heck is this slider for?

Fan speed control.

A=Auto (varies with system temperature) and M=Medium speed. I’m not sure about T, maybe Top speed? Or could it have been L=Low speed?

Cool, thanks.