Polycom RMX 1500 Administrator's Manual page 60

Chapter 1-Conference Profiles
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21 Click the Network Services check box.
The New Profile - Network Services tab opens.
Registration of conferencing entities such as ongoing conferences,
Meeting Rooms, Entry Queues, SIP Factories and Gateway Sessions
with SIP servers is done per conferencing entity. This allows better
control on the number of entities that register with each SIP server.
Selective registration is enabled by assigning a conference Profile in
which registration is configured to the required conferencing entities.
Assigning a conference Profile in which registration is not configure
to conferencing entities will prevent them from registering. By
default, Registration is disabled in the Conference Profile, and must
be enabled in Profiles assigned to conferencing entities that require
registration.