IP Office Basic Edition - 1400 Series Phone User Guide R11.1Call Handling
Adjusting the Volume
While the phone is connected to a call you can adjust the volume. The volume that gets adjusted will depend on whether you are using the handset, speakerphone or headset at the time you use this process.
To adjust the call volume: (1403/1408/1416)
1.Use the up arrow and down arrow keys to change the volume. On 1403 phones use the – + rocker button to adjust the volume.