Information Technology Reference
In-Depth Information
The proper tools are essential for anyone doing coax connector termination. A
rotary coax stripper makes preparation of the cable ends a snap and eliminates the
need for measurement. The tool has two blades that cut through the insulation to
the precise depth to expose the center conductor and the braid. Crimping the center
conductor and the outer sleeve also require the proper crimp tool. As with crimp
tools for modular connectors, the best tools are machined-die tools with a ratchet-
type action that ensures the tool is completely closed, and the sleeve or pin fully
crimped, before the handles release.
A properly crimped connector can easily withstand a moderate amount of stress
without pulling loose. If you use plenum-rated cable, be aware that the dimensions of
this type of cable are much smaller than standard nonplenum coax. In addition, plenum
coax dimensions may vary slightly with different manufacturers as the dielectric insu-
lation and jacket composition may differ. It is essential that you use coax connectors
that are designed for the style of coax you are using. Plenum-style connectors have a
smaller barrel that matches the smaller diameter of the dielectric layer of plenum coax.
The IBM cabling system was originally developed as an alternative to coaxial
cabling. It consists of two balanced pairs with an overall shield, encased in a thick
plastic jacket. The cabling system was developed to be universal, and particularly to
support IBM-centered networking systems such as Token-Ring and provide a
replacement to twin-ax, which is a single-pair shielded cable. The topology for
Token-Ring is described in Chapter 2. IBM cabling system cables are installed in
home-run configurations, and can support similar applications to structured
unshielded twisted-pair cabling. The connector used with this system is the IBM
Data Connector, which is now called the STP-A connector in TIA-568-C.
The hermaphroditic IBM Data Connector is the recommended connector for 150-
ohm shielded twisted-pair (STP) cabling systems. It has long been standardized in
IBM, ANSI, and EIA documents and was made a part of TIA-568-A.
3
The connec-
tor design, shown in Fig. B.8, is defined in IEC 807-8,
Rectangular Connectors for
Frequencies Below 3 MHz
, with additional transmission requirements in
ANSI/IEEE 802.5 (ISO 8802.5) and TIA 568-C.
3
Recognition of 150-ohm STP-A and its associated connectors was removed in TIA/EIA 568-B, other
than test methods in Sec. 11 and a brief reference in Annex D of Part B.1.