ATCOM 5520 User Manual page 34

Proxy Username: Input your SIP register account name.
Proxy Password: Input your SIP register password.
Domain Realm: config SIP local domain. If the server does not have
special requirements for the local domain of SIP terminal, the local domain
can be the same as SIP server domain. The user can also leave it as blank;
the system will take SIP server domain as the domain realm.
Enable Register: Enable or disable registration.
Register Expire Time: register expire time, default is 60 seconds. 5520
will auto configure this expire time to the server recommended setting if it
is different from the SIP server.
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