With the approval and publication of Telecommunications Industry Association (TIA)-TSB67 “Transmission Performance Specifications for Field Testing of Unshielded Twisted-Pair Cabling Systems” in October 1995, TIA launched the industry requirement for cabling system transmission performance and field-testing. Since then, it has become common practice for customers to require testing of premises cabling systems, specifically the basic link, before accepting the cabling system.
All aspects of data cabling are evolving and field-testing and cabling performance are not immune. With TIA TR42’s approval of TIA/EIA-568-B.1 (SP-4425), “Commercial Building Telecommunications Cabling Standard” in December 2000, the cabling transmission performance and test requirements have been incorporated into clause 11 and replace TSB67’s recommendations. This month’s article deals with the copper requirements, whereas next month’s will address fiber.
Clause 11 reflects the committee decision to recommend Category 5e for data cabling and to eliminate the recognition for Category 4 and 5. Category 3 remains in the document because of its recognition for voice networks, even though Category 5e is recommended. With these changes come some less-publicized changes.
First, Category 5e now means that new handheld testers, or at least upgrades, are needed. Previously, TSB67 provided for two levels of testers, referred to as Levels I and II. Very shortly after TSB67 was published, the more accurate Level II tester became the field tester of choice. However, with the additional transmission parameters specified by Category 5e, such as PSNEXT loss, ELFEXT loss, PSELFEXT loss, and return loss, Level II testers are no longer adequate, making Level IIe field-testers necessary.
Most Level II testers are upgradeable to Level IIe via a software upgrade; however, because Level II testers cannot be upgraded to test to the pending Category 6 requirements, most of the industry is shifting to new testers for both Category 5e and the pending Category 6 requirements. While Category 5e performance requirements have been approved, the final requirements for the testers are yet to be approved and are waiting for final approval of TIA/EIA-B.2, “Copper Cabling Component Standard.”
Second, TIA, in an effort to harmonize with the International Standard ISO-11801, has changed the test configuration from “basic link” to “permanent link.” The “channel” configuration remains consistent with TSB67 and the previously published Addendum 5 of TIA/EIA-568-A for Category 5e. Basic link is a very critical configuration model to contractors because it represents the installed cabling system.
What’s the difference between basic and permanent link?
The optional transition/consolidation point connector is included in the permanent link, but not in the basic link. From a performance issue, the permanent link contains three connectors, whereas the basic link only contains two. From a contractor viewpoint, if the cabling system contains the optional consolidation point, used in open office cabling systems, the test is performed from the outlet versus from the consolidation point.
The other important issue is the elimination or better-stated compensation for the cable in the test equipment cords. Previously, with the basic link, a two-meter test equipment cord was allowed at both ends for testing and this length was accounted for in the performance parameters. Now, with permanent link testing, there is no allowance for any length of test equipment cords.
In theory, the test is performed from the very back of the test plug that connects to the jack. However, this is not practical, so in essence, the field test equipment manufacturers subtract the effects of the test equipment cord cable. Most do this via software, but to properly account for the effects of the cords, they are requiring that they supply the test equipment cords. Most often, this is a fully shielded cable to provide the most accurate and repeatable test and to minimize the effects of the cable specifically for return loss.
The two above-mentioned changes have caused the performance specified for basic link to change with the requirement for permanent link.
As previously stated, the “channel” configuration remains unchanged, as do the transmission performance requirements. In theory, the above-specified performances are equal and only change because of the testing configuration change from basic to permanent. You need to ask your field test equipment manufacturer how and when they will be implementing the permanent link test configuration. Hopefully, it will only require a software upgrade and the use of the test equipment manufacturer-supplied test equipment cord.
BEAM is director of systems marketing at AMP NETCONNECT Systems. He can be reached at (336) 727-5784 or firstname.lastname@example.org.