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How To Read Cable Jackets

The world of cables has many particulars. The engineering of a cable's electrical properties and its application are usually foremost 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. Knowing how to read cable jackets is essential. 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 different cable jacket types 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
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CMCM - 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 AWG24 AWG (American Wire Gauge) - The individual conductors of this cable are 24 gauge. This does not indicate that the conductors are solid or stranded.

75C75 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.

ULUnderwriters 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.

E188630The UL reference number relates to the manufacturer of this product.

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

LL81295Just like the UL reference, the CSA reference number relates to the manufacturer.

CMGCMG - This is the rating of the fire retardant in the cable.

ETLElectrical Testing Laboratories - The standards body that verified this cable

verifiedVerified - Indicates that this cable was verified by the afore mentioned body.

TIA/EIA-568-b.2-1TIA/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 6CAT.6 - This of course indicates that this is a Category 6 network cable. Were this a coax cable, it would specify an appropriate standard like RG6, RG59 or RG59.

UTPUnshielded 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. Category 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 recommend "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 independent 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
14/2 (14AWG 2C) 105 Strand/0.16mm Speaker Cable CL3 Rated

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

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

Jacket Material

The material the jacket of a given cable is made of is one of the most important features in defining where said 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:

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

RG6 18AWG, Solid Pure Copper Coaxial Cable, 95% Copper Braid
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
RG59 Siamese Coaxial Cable, Solid + 18/2 Power, Outdoor / Direct Burial, Black

CAT5E, CMXT Outdoor / Direct Burial, Waterproof Tape
CAT5E, CMXT Outdoor / Direct Burial, Waterproof Tape

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