Information Technology Reference
In-Depth Information
for every type of cross-connect, but you can probably use a neutral color of your
choice on the wiring board. An alternative TR arrangement uses free-standing
equipment racks or rails. Cables are routed in cable trays or in bundles across the
top of the racks and down into each rack to the point of cable termination.
This is particularly useful for very large installations where much equipment
and many station terminations exist. Care should be taken in securing the cables
and cable bundles to ceilings, walls, racks, and wire termination devices. In
Category 5e/Category 6 installations, tightly binding the cables with tie-wraps
should be avoided because it may deform the cable enough to distort its electrical
characteristics. Likewise, you should maintain minimum bend radius with individ-
ual cables or with cable bundles. Avoid sharp corners and other abrasive edges.
Station wires may be terminated in the TR on a punchdown block, such as a
66M or 110-type block, or they may be terminated directly onto a patch panel (Fig.
1.8). If a punchdown block is used, cross-connect wire must be run between the sta-
tion wire termination and any other connection device, such as a patch panel. One
alternative is to use a punchdown block with a built-in connector (typically a so-
called 50-pin Telco connector). A fan-out adapter cable, often called a
hydra
or
octopus cable
, connects from the connectorized punchdown block and splits to six
(for standard 4-pair installations), eight, or even twelve 8-pin modular connector-
ized cables that can individually plug directly into a hub. To get from the punch-
down to a patch panel, a 50-pin jumper cable could be used instead of the octopus
cable. Some manufacturers also offer punchdown blocks with built-in 8-pin modu-
lar jack connections.
Although some of these devices may be certified to Category 4 or 5, they are
much more appropriate for Category 3 installations.
Direct patch panel termination is often used for Category 5e/Category 6 instal-
lations. This method provides the advantage of simple one-location termination.
There are no cross-connects, punchdown blocks, jumper cables, fan-out adapters,
or Telco connectors. All of these are potential trouble spots for Category
5e/Category 6, since each wire termination introduces “untwist” and all compo-
nents must be certified. Installation testing is also simplified with patch panel termi-
nation, because all station cables compose a Permanent Link
2
and can easily be
scanned to certification standards. The only possible disadvantage to patch panel
termination is that multiple-use applications of the station cables are difficult,
because each cable terminates into one patch panel location. Some suppliers offer
plug-in adapters with dual cable terminations, but this still limits the station cable
2
The original TIA term “Basic Link” has been harmonized with the ISO/IEC term Permanent Link,
and adjusted to match its definition. For more information, see Chapter 15.
