TPMS sensor frequency

People -

I'm in the midst of having Discount Tires set me up with a set of snows on steel rims w/tpms, and they're telling me that there's 2 (2!) different frequency choices for the TPMS - and without my car in their hot little hands (they were going to build the tires tomorrow so I could pick them up on Saturday) - they can't tell me if they have the 'right' sensors in stock, and won't go ahead building them until they know. Can't blame them, I guess

So? This sounds odd - two different frequency choices and is there any way to tell what I've got without driving an 45 miles to have them make that determination?

Thanking you guys (and gals) in advance!

 

Yeah, I don't have to tell them, but they need the car to tell. I was hoping there was something, somewhere that addressed it in the literature or onboard settings. Oh well - I'll drive down there tomorrow to get it down. Thanks for the input!