AT&T MERLIN LEGEND Release 4.0 Feature Reference page 516

Feature Reference
Notify
With Notify, a multiline telephone user can light an LED on another telephone.
To use this feature, a Send button must be programmed at the sender's
telephone and a Receive button must be programmed at the receiver's
telephone. (These buttons are typically labeled with the names of the sender
and recipient, for example, "Notify Mary" at the sending telephone and "Call
Consuela," at the receiving telephone.")
When the sender presses the Send button, a green LED turns on next to the
Receive button (at the receiver's telephone) and the Send button (at the
sender's telephone). Both LEDs remain on until the sender presses the Send
button again or the receiver presses the Receive button.
The visual notification (lighting the destination telephone's LED) is sent only one
way (sender to receiver). If both users want to send and receive the visual
notification, both telephones must be programmed with Send and Receive
buttons. Unlike the Signal feature, Notify cannot be used to see the status of a
destination extension, nor can it be used to automatically dial the extension.
Considerations and Constraints
Signal and Notify can be used even when both users are on the telephone.
Telephone Differences
Queued Call Consoles
Notify and Signal buttons cannot be used on QCCs; however, pressing a DSS
button sends a signal to the extension associated with the DSS button in the
following instances:
The QCC operator is timed out from dial tone on a Call button or presses
the Forced Release button while listening to dial tone on a Call button.
The QCC operator, in a split condition, presses the Source button after
contacting the destination but does not connect both parties by using the
Join button. If the operator presses a DSS button, a signal is sent to the
destination extension.
Other Multiline Telephones
Both Signal and Notify require a programmed button (Notify requires two). MLX
display telephone users cannot select either of these features from the display.
Single-Line Telephones
Neither Signal nor Notify can be used on single-line telephones.
516
Signal/Notify