AT&T MERLIN LEGEND System Reference Manual page 276

Features
Considerations
Responding to Messages
Single-line telephone users without a Message LED hear a recall dial tone when
a message is waiting. A single-line telephone user cannot respond to messages
by using feature codes. Normally, if a single-line telephone has a Message LED,
it is turned off by the system operator. However, a single-line user can turn off
the Message LED by lifting the handset (while listening to internal dial tone) and
dialing #54. The user must check with all message sources (system operator,
fax, voice messaging) before turning off the LED.
Posted Messges
A single-line telephone user cannot post a message.
A user does not need a display telephone to use the Leave Message feature,
but the message receiver must have a display telephone or the system must
include a voice messaging system.
Unlike Send/Remove Message, when the Leave Message feature is used to
send a message to a person whose Message LED is on, the LED is not
turned off even if the message sender is a system operator.
If a system operator uses the Send/Remove Message feature while on a call,
only an inside caller hears the touch-tones; an outside caller does not.
A display telephone can store a maximum of 10 messages. If a user tries to
send an eleventh message, the message sender hears a beep and display
telephones show the "Message Box Full" message.
Responding to messages by using Return Call does not delete the message.
The user must delete all messages before the Message LED goes off.
A maximum of four Message Waiting Receivers can be programmed for a
fax.
A fax machine can send the message waiting indication but a fax cannot be
assigned as a Message Waiting Receiver for another fax or for a calling
group and cannot receive message-waiting indications.
If a fax message-waiting indication is deleted by one of the four message
waiting receivers, the message is deleted from all analog multiline display
telephones programmed as a message-waiting receivers for the fax, but the
message is not deleted from MLX display telephones programmed as
message-waiting receivers for the fax.
Each calling group can have only one telephone assigned as its Message
Waiting Receiver, but the same telephone can be assigned as the Message
Waiting Receiver for more than one calling group.
Messages can be posted only by using a programmed button or, for MLX
display telephone users, by selecting the feature from the display. Single-line
telephone users cannot post a message.
Messaging 2-227