3Com NBX 100 Administrator's Manual page 213

Feature Group D (101-XXXX) CIC Assignments). Search the documents to
determine the identification code for your long-distance carrier. For
example, AT&T is listed next to code 288 in the Group D document.
3 From the Default Outbound Service drop-down list, select either
MEGACOM or Standard (LDS) as the service to use as the default. You
can configure the NBX system dial plan to use a particular service.
Select MEGACOM as the default service only if you purchased
MEGACOM from your long-distance carrier. You cannot select Standard
(LDS) as the default service if you purchased MEGACOM, because these
two services do not work together.
4 Click OK.
Configuring Partial T1 Lines
Sometimes the telephone company supplies a T1 line which has less than
the maximum number of channels implemented. This is called a
Fractional, Partial, or Subequipped T1. For example, you may decide to
purchase 15 channels now and implement more later in order to reduce
your near-term costs.
Some telephone companies offer Partial T1 lines as their standard
offering, and provide fully implemented T1 lines only if you make a
specific request. If you are unaware of this policy, outbound calls using
the T1 line may fail because, by default, the system places outbound calls
using high numbered channels first, and a Fractional T1 typically has the
lower numbered channels implemented.
In the Span Status dialog box, under Details of last five calls, if you see the
error message REQ_CHANNEL_UNAVAIL, determine if the error is caused
by a Partial T1:
1 Remove the highest numbered channel from service (set it to offline in
the Modify Channel dialog box) and retry the outbound call.
2 Continue to remove channels until an outbound call succeeds.
3 When the first outbound call succeeds, the highest numbered channel
still in service represents the number of active (provisioned) channels in
the Partial T1.
4 Create two groups. Put all of the active channels in one group, and all of
the inactive channels in the other. Mark the active group online and the
inactive group offline.
Configuring and Managing T1 Digital Line Cards 213