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If the outbound channel for a call will be on a different node than this one, the routing table entry specifies which NodeID that will be. It also specifies an interface or IP address to use for VTP voice traffic for that call.

There is a difference between signalling and voice. Between VX nodes, signalling is transported by way of a protocol called BSP and voice is transported by way of a protocol called VTP.

IP Networking

There are a lot of pieces that come into play when it is time to contact another VX node to use for the outbound channel and pass a call through it.

For example, a VX node 1:1:1:12 has received a call on one of its T1 interfaces. It has checked its routing table and found that the call is to be routed via BSP to node 2:2:2:42 IP/Interface 172.16.2.42

VX checks in the IP routing table for an entry that matches or includes IP address 172.16.2.42 to determine the IP interface that will be used to send information to the remote node.

At this point, VX has enough information to contact the remote node for signaling. Voice (VTP) information will use the same IP route as signaling in this case.

Calling Number Translation

These tables are similar to the call routing tables except that they don't actually alter the route taken by a call. Their sole purpose is to alter the CALLING number as the call passes through VX.

The CALLED number (the identifier of the telephone this call is trying to reach) is used for selection in the call routing tables and is potentially altered by the selected call routing entry (via the 'output' field).

The CALLING number (the identifier of the telephone this call originated from) is used for selection in the Calling Number Translation tables and is altered by a matched entry in those tables. This has no effect on routing.

Unlike call routing tables, calling number translation tables can be invoked for both the inbound trunk-group and the outbound trunk-group.

This normally only affects the caller ID presentation for the target telephone of the call. Voice mail systems may also be sensitive to the calling number in order to determine if the caller is the owner of the voice mailbox.

Tone Tables

Some TDM channels require the generation of tones by VX. Both CAS E&M and CAS R2 require this function as well as CAS Loop Start and in ISDN.
The tone tables define the specific tones used for things such as dial tones and busy signals.

R2 Mapping Tables

Many countries deploy proprietary versions of CAS R2. Typically, these versions are mostly identical to standard R2 but switch around the meanings of a few tones or bit patterns so that standard R2 devices are incompatible with them.
VX deals with these old networks via a table which remaps the meanings of the various signalling tones and bit patterns.

Only the areas where an R2 derivative deviates from standard R2 require mapping entries in this table. All tones that are not specifically remapped by the R2 mapping table are assumed to have their standard meanings.

If VX will be connecting with a system that speaks standard R2, it should require no entries in the R2 mapping table at all. The table itself need not exist. The assumed defaults should work fine.