A VoIP carrier is a service provider that can accept outgoing calls, and route incoming calls. Typically a VoIP carrier is expecting a handset to register with the carrier, and will then send calls to the registered device. It is also possible for a VoIP carrier to send calls to the FB2500 using a fixed pre-set configuration.

To set up a VoIP carrier where the FB2500 registers with the carrier you need to specify the registrar attribute. This can be a host name or IP address. You also need to specify the username and password. For incoming calls you need to specify the extn that is logically dialled when a call comes in from this carrier - this can be the extension number of a telephone or hunt group.

To set up a VoIP carrier for outgoing calls you need to specify the proxy. This can be a host name or IP address. You also need to specify the username and password.

You can define the carrer to use for outgoing calls on a per telephone basis, and also for hunt groups (where the group calls an external number). You can also define a default carrier if none is otherwise specified. A backup carrier can also be defined which is used if the call fails via the selected carrier.

For a carrier that sends calls to the FB2500 without registration, you will need to set the to attribute to either the full address used in the To: of the incoming connections, or at least the @domain part. If calls can come in to multiple numbers, you also need to set the incoming-format so that calls can be routed. In this case the username and password can be specified and are used to validate the credentials of the incoming call.

An incoming carrier will usually relate to a specific extn which is what is called when a call comes in. You can leave this unset and route based on called ddi or you can set the extn including X characters in place of the digits sent with the call as the dialled number. These are taken from the right have end of the dialled number, so if 0134567890 is what was called, 1XX would be extn 190. This makes it easy to define a trunk carrier for incoming calls.