Discovery 655/665: Power Saving Mode
Power saving mode temporarily disables the digital signal processing (DSP) feature of the Discovery headsets to provide a longer talk time. To enable power saving mode, press both the volume up and down keys at the same time before you make a call. To re-enable DSP, press both the volume up and down keys at the same time. Power saving mode cannot be turned on while engaged in a call.
Note: After you turn off the headset, DSP will be re-enabled the next time you turn it on.