AT&T MERLIN LEGEND System Reference Manual page 286

Features
Feature Interactions
Automatic Line Selection
Callback
Conference
Coverage
Direct-Line Console
Voice Announce should be disabled since the MFM does not support a
speaker.
Tip/ring devices connected on a MFM should not be used with Call
Management System (CMS).
Tip/ring applications that require a switchhook flash for operation (such as
MERLIN® Attendant, or MERLIN MAIL Voice Messaging System) cannot be
connected via an MFM since the system ignores the Switchhook flash sent by
the device.
When a Shared System Access button or a shared personal line is assigned
to the MFM, the device cannot detect when a line is picked up by the sharing
user. Therefore, if an answering machine with the built-in ability to disconnect
when another person picks up the same line is connected to the MFM, the
machine does not automatically disconnect if the user picks up a call on the
shared line that was already answered by the answering machine.
If the MFM is assigned as a primary Individual Coverage receiver, and the
MLX telephone user uses Forward or Follow Me, and if an answering
machine that disconnets when another person picks up the same line is
connected to the MFM, the machine does not automatically disconnect if the
forwarding destination picks up the call.
Single-line telephones connected to an MFM cannot use the Conference,
Hold, or Transfer features.
The Automatic Line Selection order for the MFM should be set to select Intercom
or System Access Ring, then Intercom or System Access Originate Only, and
then outside lines assigned-to the MFM, or the Prime Line in the Behind Switch
mode.
Both automatic and selective Callback can be used from an MFM; however, a
callback call cannot be manually canceled.
The Conference feature cannot be used on the MFM since the system ignores
the switchhook flash sent by the MFM.
An MFM can be a sender or a receiver for Individual or Group Coverage. This
allows the associated MLX telephone user to screen calls by using an answering
machine connected to the MFM or to supplement ringing by using an external
alert connected to the MFM. A sender can use Coverage On/Off to prevent calls
from being sent to an answering machine.
An MFM cannot be assigned as a DLC.
Multi-Function Module 2-237