Polycom RealPresence 1500 Administrator's Manual page 427

Conference and Participant Monitoring
16 Click the Message Overlay tab to send text messages to the conference participants during the
conference, and adjust the display properties of the text messages.
For more information, see Sending Text Messages During a Conference Using Message Overlay.
17 Click the Network Services tab to verify the SIP registration for the conference.
18 Click OK to close the Conference Properties dialog box.
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