Information Technology Reference
In-Depth Information
a few links failed, and it became obvious that some standard practices needed to be
created to ensure that the needed performance parameters were preserved for the
appropriate category of operation.
TSB-75,
Additional Horizontal Cabling Practices for Open Offices 1996
,
3
originally
added the rules for handling modular furniture. A Telecommunications Service
Bulletin (TSB) provides additional information and practices to supplement an
approved standard, in this case TIA/EIA-568-A. TSA-75 put down on paper the infor-
mation that installers need to properly provide standards-compliant cabling in an
open-office environment. In investigating the open-office practices that were in use, it
was determined that essentially two variations were popular and successful: providing
a location to group or consolidate cables, and placing the equivalent of a workstation
outlet at the cable grouping and running longer user cords to each workstation.
The
consolidation point
method initially terminates the horizontal cable on an
appropriate punchdown block at an intermediate distribution point between the
telecommunications room (TR) and a group of open office workstations. When it is
time to extend the link to the office module, another length of horizontal cable is
connected to the punchdown and run onto the workstation outlet.
The
multiuser outlet
method actually places the workstation outlet at the dis-
tribution point (in multiples to match the served modules) and runs an extended-
length user cord to the work area.
We will go into each of these methods in some detail in the sections that fol-
low. The provision of this standards bulletin gives the system designer and installer
the ability to provide approved intermediate interconnection points for modular
offices. Guidelines for cable length allowances that will meet the performance
requirements are given in the standard, and we will summarize these here.
Consolidation Point
A consolidation point is a point within the horizontal cable run where two cables
are interconnected (Fig. 10.3). In reality, it is a reusable connector, such as a punch-
down block, that effectively joins the two cable segments without being officially
called a “splice.” In fact, cable splices are still forbidden, presumably because they
do not allow reusability and may make poor connections when viewed from the per-
spective of crosstalk and return loss.
3
The practices in TSB-75 have now been incorporated into TIA-568-C.
