Because Customer Premise Equipment (CPE) covers a wide variety of capabilities and requires a variety of services and interfaces, the standards refer to interconnects by reference points rather than specific hardware requirements.
Reference points are a series of specifications that define
the connection between specific devices, depending on their function
in the end-to-end connection. It is important to know about these interface types because a CPE device, such as a router, may support different reference types; the reference points supported will determine what specific equipment is required for purchase.
The table in Figure provides a
summary of the reference points that affect the customer side of the
ISDN connection.
A sample ISDN configuration is shown in Figure ,
where three devices are
attached to an ISDN switch at the Central Office (CO). Two of these
devices are ISDN compatible, so they can be attached through an S
reference point to NT2 devices. The third device (a standard, non-ISDN
telephone) attaches through the R reference point to a TA. Although
they are not shown, similar user stations are attached to the
far-right ISDN switch.
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Lab
Activity |
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This
exercise will serve as a study guide to help
reinforce your understanding of basic ISDN terms and
devices to which they relate. |
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Threaded
Case
Study |
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Washington
Project: ISDN
Equipment and Media
You
need to identify what additional equipment and
media will be necessary in order to implement
an ISDN link in the Washington School District
WAN design.
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