Enhanced Full Rate
is a speech coding
standard that was developed in order to improve the quite poor quality of GSM
(FR) codec. Working at 12.2 kbit/s the EFR provides wirelike quality in any noise free and background noise conditions. The EFR 12.2 kbit/s speech coding standard is compatible with the highest AMR
mode. Although the Enhanced full rate helps to improve call quality, the codec consumes about 5% more energy and so it is recommended for use only when in a poor reception area.
You can activate Enhanced Full Rate codec in some Nokia phones by entering the following code: *3370#