ZyXEL Communications P-2612HNU-F1 User Manual page 254

Chapter 16 VoIP
When you are on the phone talking to someone, press the flash key to put the call
1
on hold and get a dial tone.
Dial a phone number directly to make another call.
2
When the second call is answered, press the flash key and press "3" to create a
3
three-way conversation.
Hang up the phone to drop the connection.
4
If you want to separate the activated three-way conference into two individual
5
connections (one is on-line, the other is on hold), press the flash key and press
"2".
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P-2612HNU(L)-FxF User's Guide