AT&T MERLIN LEGEND Release 2.0 Analog Direct-Line Console Operator's Manual page 32

About Your Direct-Line Console
To alert a co-worker of a waiting message, you can use the
Send/Remove Message feature to turn on the message light
on his or her telephone.
NOTE:
If a co-worker's message light is already on, sending a
second message turns off the message light. To avoid
this error, use the Message Status button on the
MERLIN II System Display Console to check the status of
that person's message light before you use the
Send/Remove Message feature.
1-21
Lights