Aastra Dialog 4425 IP Vision User Manual page 18

Your Extension's Accessories
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18
Notes:
You can adjust your headset listening volume in the same
way that you would for your extension's loudspeaker or
handset volume. See the
section.
When you are working with a headset, you may switch to
handsfree or handset mode by pressing the Handsfree key
on your extension, or by lifting the handset. To return to
headset mode, you must press your extension's Headset
key once again.
"Operations during a
MD Evolution – Dialog 4425 IP Vision
Call"