Finally, with the development of UMTS , EFR was refactored into a variable-rate codec called AMR-Narrowband , which is high quality and robust against interference when used on full-rate channels, or less robust but still relatively high quality when used in good radio conditions on half-rate channel.
Hatimaye, pamoja na uundaji wa UMTS , EFR ilibadilishwa kuwa kodeki ya kiwango cha kutofautiana inayoitwa AMR-Narrowband , ambayo ni ya ubora wa juu na thabiti dhidi ya kuingiliwa inapotumiwa kwenye chaneli za viwango kamili, au isiyo na nguvu lakini bado ni ya ubora wa juu inapotumiwa vizuri. hali ya redio kwenye chaneli ya kiwango cha nusu.