NEC Univerge SV8100 Features And Specifications Manual page 670

Issue 5.0
To use the headset:
 The Headset key lights when on a call. To disconnect, press the Headset key.
 You can use the handset for calls or respond to voice-announced Intercom calls with the headset plugged in. The
headset only activates when the Headset key is pressed.
Press the Headset key to answer a ringing call.

- OR -
Press the Headset key and then a line key or press Speaker then 9 to make an outgoing call.

- OR -
Press the Headset key to get intercom dial tone.

- OR -
If on a call, press the Headset key to hang up.

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UNIVERGE SV8100
Headset Operation