User Guide for the SIP-T21P IP Phone462. Select Enabled from the pull-down list of Headset Prior.3. Click Confirm to accept the change.To use headset prior feature, you should activate the headset mode in advance:1. Physically connect the headset.2. Press to activate the headset mode.NoteTwo types of DSS keys: Line Keys and Programmable Keys. The details will be introducedin the following. The SIP-T21P IP phone supports 2 line keys.You can assign predefined functionalities to the line keys to have quick access tofeatures such as call return and voice mail. The line key LEDs will indicate status whenthe keys are assigned with particular features, such as BLF. The default key type of eachline key is Line.If headset prior is enabled, the headset mode will not be deactivated until you press theHEADSET key again.Headset prior is configurable via web user interface only.