Please find the below link and reference page 10-11 (235).
Polycom HDX 3.1.1 Admin Guide
Please ensure to provide some feedback if this reply has helped you so other users can profit from your experience.
Best Regards
Glenn Davis
Polycom Global Services
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Please also make sure to check the below link for more RPM information
http://support.polycom.com/PolycomService/support/us/support/video/realpresence_mobile/realpresence_mobile_overview.html