By default, third-party SIP phones support up to 6 simultaneous calls. However, using a user source number, you can increase this to 30 calls.
The user Source Number of ULI=N allows a third-party SIP extension to consume multiple third-party endpoint licenses, where N is the number of additional licenses from 1 to 4.
Each additional license enables another 6 calls, up to a maximum of 30 calls total (4 additional licenses).
For subscription systems, the source number consumes additional user subscriptions.
Changes to the user Source Number require a system restart.
