Crestron Isys i/O TPMC-15-CH-L Operation Manual page 27

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Crestron Isys i/O
Operations Guide - DOC. 6354
TPMC-15/17-L Series
The QM transport system port is capable of managing computer, video, and audio
signals simultaneously through one Crescat-QM wire, simplifying installations.
Routing Crestron Certified Wire is less expensive and much simpler than routing
multi-colored, multi-conductor coax cable. All Crestron products using the QM
transport system are capable of sending and receiving QM signals via Crestron
Certified Wire. Installation of any QM device is as simple as installing one set of
QM wires from output to input. Installations are flexible, affordable, and fast.
The Crestron QuickMedia cable "CRESCAT-QM" contains one CAT5E cable and
®
one Cresnet cable in siamese jackets.
NOTE: Do not untwist the two wires in a single pair for more than 1/3-1/2"
(0.84 – 1.27 cm) when making a connection. The twists are critical to canceling out
interference between the wires.
CRESCAT-QM Cable
The QuickMedia transport mechanism performs delay compensation on each video
input to compensate for signal skew, and frequency/bandwidth compensation for
cable length. Signal skew occurs when part of the signal is delayed with respect to
other signal components. The amount of skew largely depends on the length and
design of the wire. Because CAT5 consists of twisted pairs that are twisted together
in the cable, unequal wire lengths are created.
NOTE: Only the QM IN 1 port features delay compensation for signal skew. For
information on maximum cable lengths, refer to "QM (QM-L versions only)" on
page 18.
The maximum aggregate cable length from QM transmitter to QM receiver is limited
by the loss of bandwidth over long distances and the amount of available skew
compensation. A cable rated at 15 ns of skew per 100 meters (328 ft.) means that a
cable will have no more than a 15 ns difference between the fastest and slowest RGB
signals over 100 meters of cable.
To determine the allowable maximum length of installed cable, the installer must
first perform a calculation based on the skew rating of the cable. The use of low-
resolution signals may allow increased cable length but must be tested with the
sources to be used. In any case, the maximum aggregate cable length should be
limited to 328 feet to prevent loss of bandwidth.
Skew compensation is primarily relevant to RGB sources; however, any/all video or
VGA signals may experience a loss of quality over very long lengths of cable. This
phenomenon is due to the added resistance and capacitance of longer cable lengths,
and is not particular to either Crestron and/or QuickMedia systems. To ensure
sufficient bandwidth to support signal resolutions up to 1600 x 1200, the maximum
aggregate cable length should not exceed 328 feet. The use of lower-resolution
signals may allow increased cable length but must be tested by the installer with the
sources to be used.
Touchpanel Media Centers: Crestron Isys i/O™ TPMC-15/17-L Series • 23
Touchpanel Media Centers