Information Technology Reference
In-Depth Information
a. The Permanent Link
Telecommunications closet
Test connector
(or adapter compatible
with horiz. termination)
Work area
Horizontal
cross-connect
2-m Test
equip. cord
Horizontal cable
(or the portion of horizontal cable
between the optional transition
point and horiz. cross-connect)
2-m Test
equip. cord
Field
tester
Field
tester
Permanent Link
b. The Channel
Work area
Telecommunications closet
Horizontal
cross-connect
Horizontal cable
Transition point
connector (optional)
Actual user's
equip. cord
Telecom. closet
equip. cord
Field
tester
Field
tester
Channel
FIGURE 15.2
The Permanent Link and Channel are defined for link testing by TIA-568-C.
when compared to ultra-expensive laboratory testing methods. So, the standard
states which tests will be done, what measured performance levels are important,
and what tester accuracy and reporting is required.
The testing that is required includes parameter measurement for the following
tests: wire map, length attenuation, NEXT loss. As more is learned about the require-
ments of networks operating at the higher levels, additional tests may be added to the
field test specifications, and others may be modified. For example, you will notice
that impedance and structural return loss (SRL) that are measured on uninstalled
cable (per TIA-568-C) are missing from this specification for installed links.
This is not because it is considered unimportant, but because it is not yet
known (or agreed) what levels are appropriate. On the other hand, the cable length,
