IP Office Basic Edition - M7310N: Call Handling
Your phone has a headset socket located under the phone. If you connect a headset, it overrides the phone's handsfree speaker and microphone and is controlled by the Handsfree button (bottom right).
•To answer a call using the headset, press the Handsfree button or the button on which the call is alerting.
•Use the Handsfree button to switch between the headset and the handset.