AT&T MERLIN LEGEND System Reference Manual page 406

Features
Group Calling
Hold
Last Number Dial
Line Request
Messaging
Multi-Function Module
Incoming calls to the calling group ring at Intercom or System Access buttons
on calling group member telephones. In the Hybrid/PBX mode, a calling group
member using a Shared System Access button is considered unavailable.
However, the principal station member can still receive calls directed to the
calling group since use of a Shared System Access button does not indicate
that the principal calling group member is on a call.
If a person uses a Shared System Access button to join a call with a person
waiting in a calling group queue. the call is removed from the queue. Both
people and the delay announcement, if programmed, are connected.
In the Hybrid/PBX mode, a call put on hold either on a System Access or Shared
System Access button can be picked up at the principal's System Access
button or at any of the Shared System Access buttons programmed for the
button with the held call (unless Privacy has been activated). Hold Reminder is
heard only by the station that put the call on hold.
In the Hybrid/PBX mode, if the Last Number Dial feature is used on a Shared
System Access button, the number is stored on the telephone that used Last
Number Dial to store the number, and not on the principal station.
Line Request cannot be used for an Intercom or System Access button.
In the Hybrid/PBX mode, if a user presses a Shared System Access button while
leaving a message for a display telephone user, the station extension of the
Shared System Access button is shown and not that of the principal station.
When a principal station user with an MLX display telephone posts a message
and a call is answered at the Shared System Access button, the calling
information is cleared from the principal station. However, the Home screen on
which the posted message is shown is not restored. If the principal station user
presses the Home button or makes or receives a call, the Home screen is
restored.
It is recommended that one System Access or Intercom Ring button, and one
System Access or Intercom Originate Only button be assigned to the MFM. At
least one System Access or Intercom button must be assigned to the MFM.
In the Hybrid/PBX mode, assigning a Shared System Access button for one or
more of a principal station's System Access buttons creates a situation where
the principal station can pick up calls that have already been answered by the
answering machine. There is no way to prevent coverage with this arrangement.
System Access 2-357