Multiple Line SIP Devices:

Some SIP devices can support multiple lines or user accounts, each configured separately. If used with an IP Office each SIP line requires a separate IP Office SIP extension, user and license. Note this refers to a SIP device that can handle multiple simultaneous calls itself and not one that is handling multiple calls by holding them on the IP Office/receiving call waiting indication for waiting calls on the IP Office. For the later, the IP Office limits third-party SIP devices to a maximum of 6 concurrent calls.

The IP Office is the SIP Registrar and SIP Proxy:

SIP extension devices are configured with separate SIP registrar and SIP proxy settings. When connecting to an IP Office, the LAN1 or LAN2 IP address on which the SIP registrar is enabled, is used for both settings.

SIP Codec Selection:

Unlike H.323 IP devices which always support at least one G711 codec, SIP devices do not support a single common audio codec. Therefore, it is important to ensure that any SIP device is configured to match at least one system codec configured on the system.

G.723/G.729b:

These codecs are not available on Linux-based IP Office systems. They are supported on IP500 V2 systems with VCM channels.

Simultaneous Calls:

Third-party SIP extensions are limited by default to 6 simultaneous calls. However this can be changed if required by associating additional third-party endpoint licenses with the extension. See Third-party SIP phone call capacity.