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Crestron QM-FTMC
Operations & Installation Guide – DOC. 6311A
QuickMedia Transport System
Using a new, proprietary signal routing solution, signals such as composite
video, S-video, RGBHV, audio, and microphone are all transported using a
single cable solution called QuickMedia (QM).
The QM transport system port is capable of managing computer, video, and
audio signals simultaneously through one CresCAT-QM cable, simplifying
installations.
Routing CresCAT-QM cable 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
CresCAT-QM cable. 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.
CresCAT-QM Cable
NOTE: Do not untwist the two wires in a single twisted 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.
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.
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. To ensure sufficient bandwidth to support signal
resolutions up to 1600 x 1200, the maximum aggregate cable length should not
exceed 328 feet.
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.
The total accumulated skew from QM transmitter to QM receiver must not
exceed 15 ns (nanoseconds). Crestron recommends a cable with a rating of less
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