3Com NBX 100 Administrator's Manual page 71

Managing Dial Plan Pretranslators 71
If the System B dial plan has a pretranslator that removes the IP address
when the call arrives at System B, (see Figure 4 on page 72), the display
panel on the System B telephone shows the calling extension and no IP
address or "*" characters. This solution works well when the extensions
on System A and System B do not overlap, for example, System A user
extensions are 1000-1999 and System B extensions are 2000-2999.
Site Codes
If the dial plan on System B uses a site code, such as 69, for VTL calls to
System A, you could create a pretranslator that prepends the site code
after it removes the IP address. (See Figure 5 on page 72.) This
pretranslator would provide caller ID information that the System B
extension can use to return a call to the System A extension. For example,
a call from System A (10.234.208.2) extension 1002 would appear on a
System B telephone's display panel as instead of
691002
. The pretranslator removes the IP address and
10*126*14*200*1002
prepends the calling extension with the System A site code, 69.
You might choose to not implement this pretranslator if calls from System
A can hop off at System B onto a PRI line because the site code would be
included as caller ID information on the PRI line, and that caller ID
information would be meaningless to someone outside the NBX system.
For hop-off calls, you could create a separate pretranslator.
VTL Calls, Caller ID and Hop Off
If a VTL call from System A to System B hops off System B and onto an
ISDN PRI trunk, the "*" characters in the caller ID string can present
problems for the PRI service. The PRI service cannot interpret the "*"
symbols so it ignores the caller ID string it has received and instead uses
the PRI line phone number. For example, if you must dial 1-508-555-1234
to get into the PRI from the outside world, that number is used for the
outgoing caller ID. If System A or System B has CLIR (Calling Line Identity
Restriction) enabled, the PRI service ignores the CLIR setting and it sends
the PRI line phone number as the caller ID.
If you have a pretranslator on System B that removes the IP address from
the caller ID string of incoming VTL calls, then the caller ID will be the
extension of the phone making the call. If system A and/or System B has
CLIR enabled, then CLIR will be in effect. The only exception is for
emergency calls (as defined in System B's dial plan), which never have
caller ID blocked.