This is for the nokia phones.It works for all the models.
There is this mode the phone can be programmed to run on, its called the HFR mode. This is The Half Rate Mode.
When this is activated, the phone automatically reduces the quality of the of the call and increases the battery life.
very useful tip, When you are out of the battery charge, Perhaps this can help your phone stay alive a little longer..
How to activate and de activare HFR:
Half Rate Mode (HFR):
*4720# to activate HFR.
Decreases call quality but increases battery life by about 30%.
#4270# to deactivate HFR.
