The world of cables has many particulars. The engineering of a cable’s

  electrical properties and it’s application is usually formost in a

  consumer’s thoughts when looking to purchase a cable. What’s not as

  frequently considered is the material used to insulate the cable. This is

  known as the jacket. Most store-bought cables are expected to be used in a

  home or office, but when buying cables for a more particular use the

  materials used in construction become more of a concern. Do you want to run a

  coax cable to your detached garage for a TV? Can you run a normal network

  cable in the plenum space in your office building? Is it legal to send this

  cable to my customer in Germany? We hope our answers to these questions, and

  more, will help make your next project a lasting success.

  The information printed on a cable jacket will usually tell you everything

  you need to know. Typically this includes the manufacturer or UPC code,

  jacket material, any electrical standards it meets, temperature rating, and

  frequently a material rating that will tell you where the cable can be run in

  a building. Let’s look at a common

  Cat-6 network cable as an example.

  Cable Markings

  Click to Enlarge

  CM – This is the material class for the cable. This is an example of a UL rating. A detailed explanation of UL ratings is given below. CM means this cable is made for general purpose. If this specified CMP or CMR, the cable would be suited for plenum or riser applications.

  24 AWG (American Wire Gauge) – The indiviudal conductors of this cable are 24 gauge. This does not indicate that the conductors are solid or stranded.

  75 degrees Celsius – This does not mean that the cable will combust at this temperature, but rather the plastics used will slowly degrade if kept above this temperature for extended periods.

  Underwriters Laboratories – This is a standards body that oversees the design and manufacture of all kinds of products. It is not part of any federal code requirements, but is sometimes required by some companies for insurance purposes.

  The UL reference number relates to the manufacturer of this product.

  Canadian Standards Association – This is another standards body like UL, but is obviously more specific to Canadian installations.

  Just like the UL reference, the CSA reference number relates to the manufacturer.

  CMG – This is the rating of the fire retardent in the cable.

  Electrical Testing Laboratories – The standards body that verified this cable

  Verified – Indicates that this cable was verified by the afore mentioned body.

  TIA/EIA-568-b.2-1 – The coloring specification for the conductors inside this cable is in EIA-568-b revision 2-1 format. For network and phone cables, this lets you know which order to put the conductors in a crimp connector or to punch down to a block.

  CAT.6 – This of course indicates that this is a Catagory 6 network cable. Were this a coax cable, it would specify an appropriate standard like RG6, RG59 or RG59.

  Unshielded Twisted Pair – Twisted pair cables offer a simple form of shielding by twisting two conductors together down the length of the cable. The number of twists per inch (TPI) in networking cable is usually around 2 to 3 TPI, but this is up to the manufacturer. Catagory specifications like Cat 5 and Cat 6 do not define cable construction, only the electrical performance after manufacture. If this were shielded cable, this would say STP for Shielded Twisted Pair. Frequently cables will also specify the percentage of the shield. Coax cables can be anywhere from 60% to 99% shields, and frequently have several layers. Many satellite TV providers reccomend “Quad Shield RG6”.

  While this information is rarely in the same order on different types of

  cables, the material ratings have the same meaning.

  UL Ratings

  The Acronym UL stands for “Underwriters Laboratory.” So what’s

  this organization and what do they do? Underwriters Laboratory is an

  independant organization that tests thousands of products under controlled

  conditions. The goal is to determine in what applications these products are

  safe to be used. The end result is recognizable standards (such as CM – see

  above) that help consumers and businesses select products that they can

  reliably count on for their specific applications. A few ratings that are

  frequently encountered in cabling are:


  14/2 (14AWG 2C) 105 Strand/0.16mm Speaker Cable CL3 Rated


  22/4 (22AWG 4C) Stranded CM Security Cable


  18/2 (18AWG 2C) Plenum Shielded Stranded CMP Security Cable, White

  Jacket Material

  The material the jacket of the cable is made of is one of the most important

  features in defining where the cable can and can’t be used. It’s

  important not only in how physically durable the cable is but also how

  resistant it is to things such as fires. Some examples of materials are:


  One of the most important considerations you can make when choosing a cable

  is selecting a cable with the appropriate shielding. If this decision is

  neglected it could lead to a poor signal or no signal at all. The culprit is

  electrical interference, electrical currents effect other nearby electrical

  currents and in the world of electronics this leads to unwanted performance

  degradation. The amount of shielding required will vary widely depending on

  what type of cable you’re using but also your application. Examples of

  when shielding decisions are necessary includes:

  A Cat5 cable being used in your home vs. in a commercial server room.

  A coxial cable being used in your living room vs. be run into your home with

  your power cables.

  Another example would be if you’re running a multimedia application over

  something like Cat5/6.

  In general whenever your cables are in close proximity to power cables a

  shielded cable should be a consideration, especially when the cables are

  running parallel to each other. Some examples of shielding include:


  CAT6, STP (Shielded), 24AWG, Solid, 500MHz, Bulk Cable, Blue


  RG6 18AWG, Solid Pure Copper Coaxial Cable, 95% Copper Braid

  Dielectric Insulators

  Cables such as coaxial cables have a dielectric insulator. The primary

  responsibility of a dielectric insulator is to keep the wire in the center of

  the cable as well as keeping a distance between the wire and anything that

  may be able to cut or pierce the jacket. The dielectric insulator is usually

  made of polyethylene or polytetrafluoroethylene. In Cat 5 / Cat 6 cables that

  are shielded Mylar is used as an insulator. Mylar is a polyester film that is

  extremely strong with excellent insulation properties.

  A good picture of a

  coaxial cable’s dielectric insulator


  Outdoor Ratings/Direct Burial

  Most cables are not inherently made to be used outdoors. A cable being

  exposed outdoors presents a few challenges which, if not addressed in the

  manufacturing of the cable, could lead to the long term failure of the cable.

  It’s important to consider the following when looking at

  outdoor-rated cables



  RG59 Siamese Coaxial Cable, Solid + 18/2 Power, Outdoor / Direct Burial, Black


  CAT5E, CMXT Outdoor / Direct Burial, Waterproof Tape

  Questions and Answers:

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