By default, when you make a call or answer a call without lifting the handset, the audio is played through the phone's speaker while you speak via the phone's microphone (not on 1403 phones).
If you have a headset attached, you can change the phone's behavior so the audio is played through the headset by default rather than the speaker.
1.Press the MENU button.
2.Use the up and down arrow keys to locate the option Call Settings.... Press the Select soft key.
3.Use the up and down arrow keys to locate the option Audio Path.
4.Use the left and right arrow keys or press the Change soft key to change the setting.
5.When completed, press the Done soft key.
6.Press the Exit soft key to exit the menus.