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TE CH N I C A L INF O RM A T I O N 258

Glossary (continued)

Ozone — Extremely reactive form of oxygen, Polyvinyl Chloride (PVC) — A general Signal — Any visible or audible indication which
normally occurring around electrical discharges purpose thermoplastic used for wire and cable can convey information. Also, the information
and present in the atmosphere in small but insulation and jackets. conveyed through a communication system.
active quantities. In sufficient concentrations
it can break down certain rubber insulations Portable Cordage — Cable with two or more Silicone — A material made from silicon and
under tension (such as a bent cable). twisted conductors for flexible applications. oxygen. Can be in thermosetting elastomer
Also called flexible cord. or liquid form. The thermosetting elastomer
Plastic — High polymeric substances, including form is noted for high heat resistance. This is a
both natural and synthetic products that are PP — Polypropylene. very soft thermoset insulation. It has excellent
capable of flowing under heat and pressure, Rated Temperature — The maximum electrical properties plus ozone resistance,
called thermoplastics. Unlike rubber and other temperature at which an electric component low moisture absorption, weather resistance,
thermoset compounds, plastics can be remelted can operate for extended periods without loss and radiation resistance. It typically has low
and reused. of its basic properties. mechanical strength and poor scuff resistance.
Plasticizer — A chemical added to plastics to Rated Voltage — The maximum voltage at Single-mode Fiber — An optical fiber
make them softer and more flexible. which an electric component can operate for waveguide in which only one mode will
extended periods without undue degradation propagate. The fiber has a very small core
Plenum — A compartment or chamber to which diameter of approximately 8 micro meters.
one or more air ducts are connected and that or safety hazard.
It permits signal transmission at extremely
forms part of the air distribution system. A RG/U — RG is the abbreviation for radio guide, high bandwidths and is generally used with
description for a cable that passes the NFPA a military designation for a coaxial cable, laser diodes.
262 (UL-910) CMP flame test requirements. and U stands for universal.
Thermoplastic — A material which will soften,
Polyethylene (PE) — A thermoplastic material Rubber (Wire Insulation) — A general term flow or distort appreciably when subjected
having excellent electrical properties. Low used to describe wire insulations made of to sufficient heat and pressure. Examples are
dielectric constant, a stable dielectric constant thermosetting elastomers, such as natural polyvinyl chloride and polyethylene.
over all frequencies, very high insulation or synthetic rubbers, neoprene, butyl rubber
resistance. In terms of flexibility, polyethylene and others. Thermoset — A material which will not soften,
can be rated stiff to very hard, depending on flow or distort appreciably when subjected to
molecular weight and density — low density Self-extinguishing — The characteristic of a heat and pressure. Vulcanizable. Examples are
being the most flexible and the high-density, material that extinguishes its own flame after rubber and neoprene.
high-molecular weight formulation being very the igniting flame is removed.
hard. Moisture resistance is rated excellent. Triaxial Cable — A cable construction having
Separator — Pertaining to wire and cable, a conductor and two isolated braid shields, all
Polymer — A substance made of many a layer of insulating material such as textile, insulated from each other. A coaxial cable with
®
repeating chemical units or molecules. The term paper, Mylar , etc., which is placed between a second braid applied over an inner jacket and
polymer is often used in place of plastic, rubber a conductor and its dielectric, between a an outer jacket applied over the outer braid.
or elastomer. cable jacket and the components it covers, Commonly used in television camera systems.
or between various components of a multiple-
Polyolefin — Any of the polymers and conductor cable. It can be used to improve Twinax Cable — Cable with two twisted
copolymers of the ethylene family of stripping qualities, flexibility or can offer conductors with established electrical
hydrocarbons, such as polyethylene and additional mechanical or electrical protection properties (one pair = two conductors sharing
polypropylene. to the components it separates. a common axis = twinax).
Polypropylene (PP) — A thermoplastic similar Sheath — Pertaining to wire and cable, the Twisted Pair — Two lengths of insulated
to polyethylene but stiffer and having a higher outer protective covering, also called jacket, conductors twisted together. Gets its name
softening point (temperature). This material that may also provide additional insulation. because two insulated copper wires are
is primarily used as an insulation material. twisted together, both of which are needed
Typically, it is harder than polyethylene. This Shield — A tape, serve or braid (usually copper, for each connection.
makes it suitable for thin wall insulations. The aluminum or other conductive material) placed
dielectric constant is 2.25 for solid and 1.55 around or between electric circuits or cables or VW-1 — A flammability rating established by
for cellular designs. Also called thermoplastic their components, to prevent signal leakage or Underwriters Laboratories for wires and cables
urethane (TPU). interference. that pass a specially designed vertical flame
test, formerly designed FR-1.
Polyurethane (PUR or TPU) — Broad class of Shield Coverage — The optical percentage of
polymers noted for good abrasion and solvent a cable actually covered by shielding material. XLP — Cross-linked poly is a thermoset and
resistance. Can be in solid or cellular form. This is cross linked by radiation, thermally,
thermoplastic material is used primarily as a Shield Effectiveness — The relative ability or by moisture. XLP offers a wide range of
cable jacket material. It has excellent oxidation, of a shield to screen out undesirable operating temperatures, excellent deformation,
oil, and ozone resistance. Some formulations interference or prevent signal leakage out abrasion, and flame resistance. XLP can
also have good flame resistance. It is a hard of the cable. Frequently confused with the be formulated with halogenated or non-
term shield coverage. halogenated flame retardant packages. Some
material with excellent abrasion resistance. It
has outstanding memory properties, making Shield Percentage — The percentage of grades are also rated XHHW-2 which offers
it an ideal jacket material for retractile cords. physical area of a circuit or cable actually excellent wet electrical properties.
covered by shielding material.

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