Polycom 3150-16966-002 User Manual page 90

For an HD conference, the system does not provide the message overlay function.
•
The message overlay set at the Participant Properties page supersedes any
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message overlay set on the Conference Properties page. When the two settings
conflict with each other, the message overlay on the participant's endpoint screen
is displayed as follows: The participant's message overlay, even if set later than
the conference overlay, immediately replaces the conference level message
overlay. The conference level overlay will not be displayed until the participant
level overlay is finished displaying.
Polycom RMX 1000 User Guide
9-11