First choose the CONFERENCE option for one line.
Then SWITCH CALLS to the other line.
And put the other line in CONFERENCE mode.
OPTIONS
SPEAKER
RELEASE & HOLD
SWITCH CALLS
CONFERENCE
OK
EXIT
OPTIONS
SPEAKER
RELEASE & HOLD
SWITCH CALLS
CONFERENCE
OK
EXIT
OPTIONS
SPEAKER
RELEASE & HOLD
SWITCH CALLS
CONFERENCE
OK
EXIT
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