I know only enough about this stuff to keep myself from getting shocked (too often), but I don't think I'd be too far off to say that in order to get both your low & high beam wires to operate on this two-wire transformer and to make that LED shine at two separate brightnesses, you will have to have, at the very least, one resistor - that will wire into your low beam 12V supply - and at least one diode to be places between your two 12v supply wires in order to keep your low beam wire from backfeeding into your high beam supply wire and activating it's blue indicator light. Unfortunately, it's going to take someone smarter than me to determine which resistor will reduce that low beam wire enough, but not too much, to allow the LED to shine just right.