Cable Testing; Equalizing Pair Skew - Extron electronics TP Receivers User Manual

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Cable testing

To ensure proper cable termination, each transmission cable
system using CAT 5e should be tested (Extron's Enhanced
Skew-Free 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 are important indicators of the quality of the
cable termination, the most critical testing parameters for video
transfer are wire map (T-568-A 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 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

The manufacturing process for network (CAT 5e) UTP cable leads
to a condition called pair skew. For best results, pair skew needs
to be equalized when using the CAT 5e cable in A/V applications.
The design of the Extron Enhanced Skew-Free A/V UTP cable
reduces pair skew to the point that equalization is not required.
TP Receivers • Installation and Operation
Enhanced Skew‑free A/V cable is not recommended for
Ethernet/LAN applications.
This cable is specially designed for compatibility
with Extron's Twisted Pair products, wired using the
TIA/EIA 568 A standard.
The green, brown, and blue pairs of this cable have
virtually identical lengths, and should be used to
transmit the RGB signals.
The orange pair of this cable has a different length and
should not be used to transmit RGB signals.
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