Nortel BCM 3.7 Manual page 477

Conference calls A conference call cannot be parked on a SWCA key.
You cannot conference a call that is parked on a SWCA key. To conference
such a call, you need to retrieve the call, and then put it on hold, and then
create the conference.
If a conference call is created from two SWCA-associated calls, and then a
transfer occurs by the conference master releasing, the remaining call
between the two conference slaves will move to being associated to only
the currently associated SWCA keys (if any) on the slaves.
If a conference call is created from two SWCA-associated external calls,
and then a transfer occurs by the conference master releasing, the
remaining call between the lines/trunks will not be associated with any
SWCA keys.
Hold Only active calls can be assigned to SWCA keys. If you want to move a
call on hold to a SWCA key, you must un-hold the call, and then assign the
call to a SWCA key.
Your system administrator can set a SWCA system control to force a call to
attempt to assign to a SWCA key when you press hold for an active call. If
the call cannot be assigned to a SWCA key, such as the case where all keys
are already assigned, the call remains on hold at your telephone.
Auto hold If auto hold is enabled for the telephone, and you press a SWCA key with a
parked call while you are still on an active call, the active call will
automatically be put on hold at your telephone, assuming that an intercom
resource is available for the call.
If auto hold is not enabled for the telephone, and you press a SWCA key
with a parked call while you are still on an active call, the active call gets
dropped.
You can change this setting at the telephone using FEATURE 73 to enable
the feature or FEATURE #73 to disable the feature. Or your system
administrator can change the setting through the Unified Manager under
Capabilities for each telephone.
Configuring system-wide call appearance groups
Programming Operations Guide
477