Sony SPP-M937 - Manual (Page 34)

34 US Advanced Features
Having a conference call
You can talk on two lines at the same time and you can also talk on
one line, the handset and the base phone at the same time.
Making another call while talking
You can talk with two parties at the same time using both line 1 and
line 2. (Three-way conference)
1
Press (HOLD) while talking on
one line.
The line in use is put on hold.
2
Press (LINE 1) or (LINE 2),
whichever is not used.
3
Dial a phone number for the
second party.
4
Press (CONF) (conference) after
the second party is connected.
Now you can talk to both
parties.
(CONF)
(HOLD)
(OFF)
(LINE 1)
(LINE 2)
(OFF)