Information Technology Reference
In-Depth Information
TR
WA
ER
Equipment Room
x
HC
Horiz. Cross-connect
HC
IC
Intermediate Cross-connect
MC
Main Cross-connect
TR
Telecommunications Room
WA
TR
ER
WA
Work Area (Outlets)
x
Cross-connect
x
x
HC
IC
x
MC
WA
TR
ER
x
x
HC
IC
FIGURE 14.1
The structured wiring hierarchy includes the telecommunications room (TR), the intermediate
cross-connect (IC), and the main cross-connect (MC).
Cross-connections would be made between the LEC lines and the telephone
switching equipment and additionally between the telephone switch and large mul-
tipair cables running to the ICs or TRs on each floor. A large building would have
intermediate cross-connect (IC) spaces where the multipair cables would be termi-
nated and split out to other feeder cables to TRs near various office locations. At
the TR, the station cables from each workplace location would be cross-connected
to the feeder cables. The line for each phone would actually be connected through
the TR, to the IC, to the MC, and finally to the telephone switch. In a smaller build-
ing, the functions of the various closets may be combined. In a very small building,
all connections might be made in one space, a combination TR/MC/ER.
Fitting LANs into the Structured Cabling Heirarchy
LAN wiring is implemented on basically the same scheme, but with several impor-
tant differences. First, LAN systems are distributed systems. There is no large cen-
tral device similar to the PABX from which all the connections emanate; instead, the
connections are made to hubs located in the telecommunications room (thus a
TR/ER). Then, as we will see, the hubs are interconnected to each other and to com-
mon resources such as servers.
With regard to LANs, telecommunications rooms are usually interconnected
with no regard to hierarchical level, since the network components are distributed.
Still, the telecommunications room hierarchy is a useful model.
