AT&T MERLIN LEGEND Release 4.0 Feature Reference page 362

Feature Reference
Telephone Differences
Direct-Line Consoles
An MFM in a Direct-Line Console (DLC) serves only as another extension,
without the characteristics of the operator extension.
Queued Call Consoles
An MFM cannot be connected to a Queued Call Console (QCC).
Other Telephones
An MFM can be installed only in MLX telephones and cannot be used with
analog multiline telephones.
An MFM cannot be used with a terminal adapter or desktop video system.
Single-Line Telephones
A single-line telephone or other type of tip/ring device up to 1000 feet away can
be connected to the MFM and used to make and receive inside and outside
calls.
A single-line telephone connected to an MFM cannot use the Pickup,
Conference, Hold, or Transfer features.
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Multi-Function Module