Example.....extension 102 calls extension 101 and 102 presses the soft-key [MSGW] which turns the light on at extension 101.
The message waiting light at extension 101 stays on until 101 calls back the extension that turned it on (102).
To extinguish the light at extension 101, simply dial the person who light the light at that phone.
It should say in the display with several arrows ( >>102 )
You can turn another extension's message waiting light on from your extension