Hi,
The SPA9000 supports up to 16 IP telephone registrations.
I suspect that you are looking at the web-ui > Voice tab > Line N tabs
These lines are used to register the SPA9000 to ITSPs or gateways such as the SPA400.
This is described in the Configuring Line Interfaces on the SPA9000 starting page 58 of the SPA9000 Admin Guide located at https://www.myciscocommunity.com/docs/DOC-1750
Here's an excerpt for you:
You can configure the following types of services on the SPA9000 line interfaces:
Up to 16 DID numbers can be supported on each line interface. You can configure different ITSP accounts on different line interfaces.
You can configure a line interface to register the SPA9000 with a SPA400 to support PSTN lines.
- SPA400 voice mail service:
You can configure a line interface to register the SPA9000 with a SPA400 to support voice mail server. This SPA400 should have no more than two PSTN lines connected. If more than two PSTN lines and voice mail are required, you should reserve one SPA400 exclusively for voice mail. Exceeding these guidelines will affect the quality of voice mail playback and command recognition.
You can configure a line interface to register the SPA9000 with a Mediatrix® 4400 ISDN BRI Digital gateway.
Regards,
Patrick
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