Nortel T7406 - Manual (Page 49)

Optional accessories / 49
T7406 Installation Guide
Headset installation
Follow these steps to attach a headset to the handset port.
1. Lift up and remove the rubber tab to expose the headset port.
2. Insert the headset jack into the headset port.
Note: The headset jack has a 2.5 mm opening. An adapter
may be required if your headset has a 3.5 mm pin.
The handset microphone and earphone are disabled when the headset is
connected to the headset port. If you use the headset, use the Options
button to answer calls and to use the Options List to customize features.
When you remove the headset from the headset port, handset operation
is enabled automatically.