AT&T MERLIN LEGEND System Reference Manual page 277

Features
Feature Interactions
Barge-In
Directory
Direct-Line Console
Direct Station Selector
Display
2-228 Messaging
Posted messages are only seen by multiline display users. Users with single-
line telephones or multiline telephones without a display cannot see a
message posted by another user.
Posting a message does not prevent the telephone from ringing.
If a blank message is programmed via system programming, the user is not
prevented from posting the blank message. However, callers with display
telephones see nothing on the display to Indicate that a blank message is
posted.
If, while posting a message, a user responds to a message by using Return
Call, message posting is ended and the message is not posted.
The 5-button analog multiline telephone has neither a Message LED nor a
Message button. To use Messaging, the user must program the feature onto
a button.
If Barge-In is used to contact a user with a posted message, the caller's
telephone does not display that message.
When an Extension Directory is used to call a co-worker with a posted message,
the posted message is not displayed on the caller's telephone.
The Send/Remove Message feature is a system operator-only feature used by
the DLC system operator to turn on the Message LED to indicate a message
waiting. For telephones without a display, Send/Remove Message is the only
way the Message LED can be turned on and off by system operators.
A Send/Remove Message button is factory assigned to an MLX-28D used as a
DLC. When a system has fewer than 29 lines connected, Send/Remove
Message is factory assigned to analog DLCs with 34 buttons or more. The
Send/Remove Message button is replaced with line 32 when the system has 32
lines or more. Send/Remove Message is not a fixed feature and can be
assigned to any available button on either an analog or MLX DLC.
When a system operator presses the Message Status button on a DSS adjunct,
the LEDs on the DSS reflect only messages left by a system operator using the
Send/Remove Message feature and not messages left by any user (including a
system operator) using the Leave Message feature.
When users try to send a message to a telephone whose message box is full,
they see "Message Box Full" on the display. When a user tries to retrieve
messages and the message box is empty, "No Messages" appears on the
display indicating there are no messages.