Information Technology Reference
In-Depth Information
copper wire is 4-pair, 24 AWG cable, while the fiber is 62.5/125 µm cable. Eight-pin
modular connectors are used for the copper, and ST connectors are used for the fiber.
The basic layout of a telephone-style wiring plan assumes that there will be
hierarchical cross-connect points where large-pair count cables are terminated and
fanned out into smaller cables or to station cables.
The length of individual runs and the number of cross-connect points are not
critical because traditional telephone equipment can run much longer distances than
LAN cable.
PDS uses the 110-block as the basic cross-connect component. Station outlet
modules use insulation-displacement connectors that snap into a modular faceplate.
All connectors are normally specified as 8-pin RJ-45 style connectors, although 6-
pin RJ-11/12s are also available. The connector modules are available with mark-
ings for “Data” or “Voice” and the rears of the modules are color coded to the wires
of the 4-pair cable. The Avaya/Lucent (AT&T) color code and pin mapping are
shown in Table 3.2. Note that the standard wiring pattern for the PDS 8-pin mod-
ular jack is identical to the T568B pattern of TIA-568-C. This is not a coincidence,
as the influence of standard telecommunications wiring plans, such as PDS, carried
great influence in the design of the EIA-TIA standards. An earlier Western Electric
plan, referred to as Distributed Inside Wire (DIW), was a logical precursor to both
PDS and the EIA/TIA systems.
In the 1980s, IBM Corporation designed a multiuse cabling system to support the
rapid introduction of twisted-pair wiring for computer networks.
The cabling system uses a unique hermaphroditic connector (called the Data
Connector) and several types of cable identified by a simple numbering system.
Figure 3.3 shows a picture of a Data Connector, and Table 3.3 lists the cable types
and their characteristics. The cable types, designated Type 1 through Type 9, include
STP and UTP cables, as well as combinations of both.
The concept behind the IBM cabling system is that most workstation locations
actually need at least one data circuit and one telephone circuit. Both needs could
be provided by one cable, such as a Type 2 cable, with shielded pairs for the data
and unshielded pairs for the telephone.
The cabling system uses a clever genderless connector that eliminates the need
for two complementary connector styles (such as the plug and jack of modular
wiring). Data connectors simply plug together to make a connection. This requires
that the identical style of connectors be used at the cable end, wall plate, and patch
panel. The unique Data Connector was probably designed with Token-Ring in
