Complex sentence: Vrataski forces Carter to explain to Cage that during his employment at Whitehall General Brigham supervised the construction of a prototype transponder Carter built which can theoretically ascertain the location of the Omega if injected into an Alpha Mimic or someone with the reset ability.
Split into simpler sentences: Vrataski forces Carter to explain to Cage that during his employment at Whitehall General Brigham supervised the construction of a prototype transponder. Carter states the device can theoretically ascertain the location of the Omega if injected into an Alpha Mimic or someone with the reset ability.