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COMSPHERE 3000 Series Carrier
3-38 December 1994 3000-A2-GA31-80
Make sure that all devices installed in each half of the
carrier are configured with compatible digital/leased-line,
dial/dial backup, or switched 56 kbps backup interfaces.
All devices installed in a particular carrier half must be
capable of interfacing to the leased-line network, dial
network, or switched 56 kbps digital service using the
common interface connections on the rear of the carrier
(see Figure 3-27). The digital/leased-line interface is
provided through a 50-pin connector, while the dial/dial
backup and switched 56 kbps backup interfaces are
provided through Network Interface Modules (NIMs).
The dial/dial backup interface NIMs are available with
either Permissive or Programmable mode. The switched
56 kbps backup interface is provided through one of the
Switched 56 NIMs, either the 2-wire or 4-wire version. A
NIM must be selected for half a carrier if any devices in
that half of the carrier use the dial backup or switched
56 kbps backup interface. The NIM selected defines the
pinouts of the dial or switched 56 kbps connection for all
devices within that half of the carrier.
When devices are mixed, it is recommended that they
be clustered together, and that dial/lease modems be
installed from the left, starting with Slot 1.
• When dial/lease modems are mixed with DSUs in
the same half of the carrier (i.e., Slots 1–8 or
Slots 9–16), the dial/lease modem’s leased-line
connection may not occur on the proper pins;
therefore, cross-connection may be required at the
network interface.
• When populating the same half of the carrier with
all DSUs with dial or 2-wire switched 56 backup
capability, the DBM network interface module
(NIM) is used. When populating it with all
dial/lease modems or a combination of DSUs with
dial backup capability and dial/lease modems, the
DDD NIM must be used. Both NIMs are available
in permissive or programmable versions. In
addition, when populating it with all DSUs with
4-wire switched 56 kbps backup capability, the
4-wire Switched 56 NIM must be used.
The remainder of this section provides the following
information:
• Digital or analog leased-line network interfaces
• Dial network interface
• Switched 56 kbps network interface
• COMSPHERE 3811 control interface
A number of possible interconnection schemes are
available from the network interface connections to the
network interface.
Figure 3-28 illustrates the cabling connections for a
dial/lease modem, such as the Model 3811 or 3911.
Figure 3-29 illustrates the cabling connections for a
DSU or a DSU with a V.32 or 2-wire Switched 56 DBM.
Figure 3-30 illustrates the cabling connections for a
DSU with a 4-wire Switched 56 DBM.