Avaya 1200 - Manual (Page 140)

While on an active call
140
To use call conferencing:
1. Enter the first phone number or SIP
address that you want to call.
2. Place the active call on hold.
3. Make a second call.
4. When the second call is connected,
choose one of the following methods to
establish a conference call:
Conf — Press the Conf soft key and then
press the line button of the first held
call.
OR
Feature — Press the Feature soft key.
— Enter 3 on the keypad.