Message Led - так называлось, и никакой настройки по типу не было.
Из доки
Normally, the voice mail system is connected to proprietary station ports on the system. This
allows for full integration in most modern systems, which means that the built-in message
waiting light on the electronic phones will light whenever there is a message for that phone.
The technics used for analog phones on Alcatel PCXs consists in switching the ringing signal
(with a dedicated –15 dBm0 default Tone) for a short period of time . As a result, the LED of
the phone will light but w/o turning the Ring on.
This solution doesn’t allow to interwork with Neon MSG lamp phones or with what’s known as
“high voltage” Message lamp phones. High voltage message lamp phones require a DC
signal of 90 to 140V DC on the line while the phone in idle.