Extron electronics Twisted Pair Receiver VTR001, Руководство пользователя

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VTT001 and VTR001 • Installation
Installation, cont’d
2-8
Cable testing
To ensure proper cable termination, each transmission cable
system that uses CAT 5e or CAT 6 cable should be tested
(Extron Skew-Free A/V UTP cable does not need to be tested).
Testing the cable from the RJ-45 connections at the transmitter
and receiver gives the most accurate indications of cable
problems.
There are two varieties of cable runs: simple runs, in which a
single cable is terminated only at the transmitter and receiver,
and complex runs, which can include patch bays and multiple
terminations and lengths of cable. In either case, the entire
cabling system should be tested.
A complete test measures cable length and tests the wire map,
attenuation, NEXT, PSNEXT, ELFEXT, PSELFEXT, return loss,
ACR and PSACR. All of these tests are critical for digital data
transfer. While all of these tests are important indicators of the
quality of the cable termination, the most critical testing
parameters for video transfer are wire map (T568A or T568B
termination) and pair length measurements. The largest
concern is equalization of skew between cable pairs. Cable
systems of 300 feet or less should exhibit no transmission
problems if they pass at least CAT 5e or preferably CAT 6-D5
channel certification testing.
The Microtest OMNI SCANNER 2 performs comprehensive
certification testing to the proposed CAT 6 standards. Other
manufacturers also make testing equipment. The tests include
advanced diagnostics for troubleshooting the cause and location
of many cable and termination problems. For simple
installation testing, the Microtest MICRO SCANNER PRO tests
wire map and cable length, including individual cable pair
length.
Equalizing pair skew
Pair skew issues are eliminated when you use Extron
Skew-Free
™ A/V UTP cables.
The manufacturing process for CAT 5e or CAT 6 network UTP
cable leads to a condition called
pair skew . For best results, pair
skew needs to be equalized when using the CAT 5e or CAT 6
cable in A/V applications. The design of Extron’s Skew-Free
A/V UTP cable minimizes pair skew to the point that
equalization is not required.
Skew exists between pairs when the physical length of one wire
pair is different from another. As the transmission cable length