2
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Functional Design
NetXpress LX & CM-30R Installation & Operation Manual
Version 1.1
GatesAir, Inc.
2-11
Intraplex Products
2.5.2
TDM Channel Loopbacks
Figure 2-3 shows the normal/default of no loopback and the three Time Division Multiplexing (TDM)
channel loopback scenarios for channel modules and TDM busses: internal, external, and both.
Figure 2-3. TDM Loopback Scenarios
When you apply the internal loopback to a time slot or a group of time slots on the TDM bus, the
channel module data is copied back to the receive channel on that same TDM bus, as well as being
transmitted to its IP targets. When you apply the external loopback to a time slot or a group of time
slots on the TDM bus, the received data is delivered to the channel module on that same TDM bus as
well as being transmitted back out to its originating source. You can apply both internal and external
loopbacks simultaneously. This example shows loopbacks for an entire bus. However, you can also
loopback individual time slots within a bus.
2.5.3
TDM Bus Mapping
The NetXpress LX or CM-30R TDM bus is connected by default to a virtual IP bus; this connection is bi-
directional. The TDM bus mapping feature allows you to reconfigure your connections to suit your
needs. You can connect a time slot from TDM A, TDM B, or either of the echo cancellers to the
corresponding time slot on any of the 4 IP ports. You can connect a time slot from TDM A or TDM B to
the corresponding time slot on either of the echo cancellers.
The NetXpress LX system (or CM-30R module) has 2 bus map choices:
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The pre-configured default map has both TDM A and TDM B busses mapped from IP sources to
two (multi-unicast) IP destinations (connections).
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You can select the User Defined Profile and create a customized bus map configuration. For
example, you can create a multi-unicast configuration, where one source is connected to more
than two destinations. Section 4.3.3.4
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TDM Bus Mapping Configuration
gives additional multi-
unicast information.
