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Cable Understanding The Important Facts

This information below is for the benefit of installers, engineers and end-users in understanding some of the key points behind low voltage telecommunications cables whether Ethernet or coaxial cable types. For any given point below it is possible to elaborate at a much deeper level although this should allow for a better basic understanding of the key points.

Industry Certification and Approval Agencies

Manufacturers or resellers of cable can make any claim about cable specifications or performance. How can a buyer or end-user be assured of these claims? 

There are two primary factors that buyers or end-users should be aware of:

A.      Safety

1.       This is for protection in the event of a fire and involves flame burn tests.

B.      Performance

2.       This is to insure electrical performance.

The two competing Nationally Recognized Testing Laboratories (NRTL) are:

A.      Intertek

B.      Underwriter Laboratories (UL)

Safety marks from these agencies are:

A.      UL Listed (UL)

B.      ETL Listed (Intertek)

Performance testing (LAN Cable) marks are:

C.      UL Verified

D.      ETL Verified

Critical Recommendation: Unfortunately there are many reseller types whom buy cable from China and falsely claim safety listings and/or verified status. Often you will find mention on a website in the product description or specification of this, on a drawing, on the cable reel or box or on the cable jacket itself. If these folks get caught and investigated they will be in serious legal troubles, not only from the approval agencies, but from unsuspecting buyers whom have installed the cable. Thus we recommend that you always check the UL or Intertek databases to see if the company name appears with the certification. To facilitate this check, we have a UL and ETL symbol at the bottom of every webpage on our site that can be clicked on and you will automatically be taken to the corresponding database. A few moments of your time can insure you won’t be on the line for a bad buying choice!

What is required for a manufacturer to get UL or ETL Listed / Verified?

Manufacturers must submit cable samples for testing and agree to follow-up plant inspections. Fees are paid to these agencies for this effort. The testing insures that the cable meets the minimum requirements.

Why is LAN verification important?

LAN Ethernet cables must meet minimum requirements depending on whether they are category 5, 5e, 6, etc. The requirements for these categories come from the detailed performance specification defined by the Electronic Industries Association / Telecommunications Industry Association, otherwise known as the TIA/EIA. The TIA/EIA 568-C standards define numerous criteria such as specific checks of resistance, capacitance, crosstalk, return loss and propagation delay.

What happens if a cable is utilized that doesn’t meet the TIA/EIA 568-C requirements?

Simply stated, the performance would be inferior. For example, the Category 5e cable specifications assure the transmission rate of 1 Gigabit (1000 Mbps). However if the various electrical values do not meet the requirements, the transmission rate could not be supported. Furthermore in data transmissions, there are error checks, which result in re-transmissions causing higher bandwidth usage resulting in inferior performance. While this might be a bit difficult to describe to a non-engineer, it can be more clearly visualized as in a video transmission over the data link. The following photos which were courtesy of Anixter at a 2011 Bicsi Conference show the use of an unverified cable on the left versus a verified performance cable on the right. The blurry photo on the left is a result of the inferior data transmission caused by patch cables which did not meet the TIA/EIA 568-C minimum requirements.

The same conference reported that 379 category 6 patch cables were purchased from lesser known manufacturers and tested. Of these, 322 or 85% failed to meet the near end cross talk (NEXT) requirements. Interestingly 78% of the failed samples failed by a margin of 3 dB or more and 45% failed by a margin of 6 dB or more!

Critical Recommendation: Always be sure to double check and verify with the verification agency that the horizontal, vertical or patch cables that you are purchasing have definitely been verified against the TIA/EIA 568-C.2 standards. Also always buy from a manufacturer who has a reputation for strong ethics and honesty. Why put your job, your company and your customer at risk to save a $1.00? It doesn’t pay in the long run.

What are some of the other types of things should we look out for?

Many dishonest players are selling cable under false specifications. For example, there is a cable in the worldwide market know as copper cladded aluminum (CCA). It was advertised and sold for example as 24 AWG solid copper. However this is an aluminum wire coated with copper. This is non-approved under the EIA 568-C.2 standards and particularly dangerous when used in power-over-Ethernet (PoE) applications.

However, if you are insuring that you are buying either UL or ETL verified cable against the EIA 568-C.2 standards, then you are safe against these types of suppliers.

Often cable is advertised with a number like 350 MHz. Is this important to consider?

The TIA 568-C.2 standard requires testing, whether by UL Verification or ETL Verification, at the following:

 

Required Testing Parameter

Cable Category

Supported Network Application

100 MHz

Cat5e

1 Gigabit (1000BASE-T)

250 MHz

Cat6

1 Gigabit (1000BASE-T)

500 MHz

Cat6A

10 Gigabit (10GBASE-T)

 Many manufacturers or sellers of cable push MHz ratings to unwitting buyers in order to generate a premium price or to have you believe that their cable is somehow better. Many of these cables don’t support the higher ratings or haven’t actually been tested at these values. There is no independent testing by UL or Intertek verification programs for these values. Nor would the higher rating provide any value even if it were true. Other criterion of the cable specifications only allow for a certain network application for a given cable category anyway.

Critical Recommendation: Never buy cable based on MHz ratings. It is a marketing gimmick and not relevant. Always chose a cable based on the intended network application and for its quality, i.e. the safety listing and verification status.

What are the different NEC jacket types (primarily indoor cable)?

The National Electric Code (NEC) defines the jacket types. The UL or ETL Listing programs verify that a cable jacket meets the requirements.

 

Rating Designation

Designated Use

NEC Article Reference

Test Requirement

CM

General Purpose

800.179(D)

ANSI/UL 1685

CMG

General purpose, with the exception of risers and plenums

800.179(C)

 

CMR

Suitable for use in a vertical cable run in a shaft or from floor to floor.

800.179(B)

ANSI/UL 1666

CMP

For use in ducts, plenum air returns.

800.179(A)

NFPA 262-2007

CMX

Limited use – intended for residential use where some cable is installed internally and some on outside walls. Note: This is not an accepted general use outdoor cable.

800.179(E)

ANSI/UL 1581 VW-1

 

Are there any NEC types for UL or Intertek Listing of outdoor cables?

The NEC does not require listing on outdoor low voltage cables, coaxial or Ethernet. Thus the UL or Intertek do not have a standard for listing purposes on outdoor cables. Therefore you have your options or choice on the outdoor cable selection.

Since outdoor cable would not normally have an UL or Intertek (ETL) Listings or Verifications, then is there any way to easily identify non-professional cable sellers, i.e., those folks just reselling some cheap Chinese cable?

Yes. With just basic knowledge pointed out in the document, one can easily spot these types of sellers. We examine two live examples below:

1.       “Cat5e, 350 MHz, UTP, UV Jacket, Outdoor, CMX, 1000ft, Black, Bulk Ethernet Cable, Wooden Spool” and “ETL type CMX for outdoor network installations” were seen on one website.

a.       Of course there is no proof that this cable would perform at 350 MHz and there is no value of 350 MHz in a Cat5e cable and network. Just a marketing gimmick.

b.      It proposes that this is a CMX and outdoor cable. CMX again is a limited use cable for use on residential dwellings where the cable runs along the outside of a wall and then back inside. CMX does not imply use as a general outdoor cable. Also a CMX cable would normally be produced in beige or other neutral color for use on the outside wall of residential dwellings. This cable is black.

c.       It states ETL type CMX for outdoor. Again, non-factual information and misleading information is presented. In the United States the majority of cable tested for safety against NEC building codes is done by UL, not Intertek (ETL). The Intertek ETL is more often used for performance and this would be ETL verified against the 568-C.2 standards.

  1. "Black 1000-Foot CAT5E Outdoor Direct Burial CMX Cable, Poly-Gel Filled and Shielded, 24AWG, LSZH Jacket, 4 Pairs, Solid” This one also lists the specifications as “350MHz, 24 AWG, UV-Protected, Shield Twisted Pair, Poly-Gel Filled, Outdoor Aerial/Duct Cable, LSZH Jacket, CMX Cable".
    1. Again CMX is a limited use outdoor cable to be installed on the side of residential dwellings and partly inside. It is definitely NOT an outdoor or direct burial cable!
    2. Furthermore it indicates poly-gel filled. The gel would have flammable characteristics and would never pass CMX flame tests in the UL or Intertek laboratories. So another reason this is just nonsense marketing material by non-engineers simply reselling cheap quality cable.
    3. This one also purports 350 MHz, which is of no value in a 350 MHz cable.
    4. Even crazier, it lists it as LSZH, which is low smoke zero halogen, which has been largely a European requirement. There is no NEC specification for this, thus there is no UL or Intertek Listing program for this type of jacket. A LSZH jacket is for indoor use where concern over low smoke and zero halogens are concern versus flame height as in NEC codes. Some of these sellers have no idea of what these basic terms mean. And to think that people buy cable from them!

What are the jacket material options for outdoors?

The common jacket types are: polyethylene (PE), polyurethane, and thermoplastic elastomer (TPE). The PE type is the most common with excellent electrical properties, moisture resistance, abrasion resistance and a wide temperature range support. Indoors it would be common to use PVC; however this does not have long term survival ability in outdoor environments.

What do the acronyms UTP, FTP and STP refer to?

UTP - This is unshielded twisted pair, 100 ohms and is the most common networking cable.

FTP - This is foil twisted pair. This has an overall aluminum foil which protects against electromagnetic interference (EMI) from entering or exiting the cable. This cable has a 100 ohm impedance.  

STP – Shielded twisted pair. This cable has a shield around each pair in the cable and originates from the IBM cabling specification with 150 ohm impedance. In scouring the Internet, you can find resellers of low price Chinese cable stating is STP, when what they are selling is likely FTP, with 100 Ohm impedance.

S/FTP – This variation has a foil shield around each pair + an overall foil around all pairs and is a 100 ohm impedance cable.

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