Interphase Tech iSPAN 5535 PRI - Manual (Page 38)

North America T1/PRI Line
18 Interphase Corporation
If the distance is longer (up to 6200 feet or 1800 meters), you
need to connect the adapter in a DS1 configuration. In this
configuration, a Channel Service Unit (CSU) must translate
the short haul DSX1 interface in order to support the longer
distance.
The iSPAN-PRI adapter optionally supports an internal CSU.
In this case, you can connect the adapter directly to the T1/PRI
line, also in a DS1 configuration. If your adapter does not
include this option (and if the distance is too long), you will
need to connect the adapter to an external CSU, which itself
will be connected to the metallic T1/PR1 interface.
Connecting directly to the line without a CSU
You can connect the iSPAN-PRI directly to the line without
any internal or external CSU if the distance to your carrier is
short enough (less than 655 feet or 200 meters). The line will
be in a DSX1 configuration (short haul). See Figure 3-1.
Figure 3-1. Adapter connected directly to the Telco
Direct connection is subject to constraints imposed by FCC
rules and by your partner carrier. For more information about
these constraints, and to find out if you can connect directly to
the interface, contact your carrier.
WAN Adapter Telco
Less than 655 feet (200m)