Discovery 655/665: How to Disable DSP
How do I disable Digital Signal Processing (DSP) on my Discovery 655/665 Headset?
Power saving mode temporarily disables the Digital Signal Processing (DSP) feature of the Discovery 655 and 665 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.