Crestron electronic QM-FTCC - Manual (Page 42)

QuickMedia™ FlipTop Computer Center Crestron QM-FTCC
Appendix B: QuickMedia Installation and Compensation
Installation Notes
You must pass audio through from transmitters to receivers even if you are not using
the audio signal. The information required for auto-compensation is transmitted
along with the audio. In addition, the QM Link signal indicates that the QM cable is
connected and that an audio signal is present on the cable. If a unit does not receive
an audio signal, the QM Link signal will not go high and a valid QM Link
connection cannot be detected (video can still be displayed if auto compensation is
not used).
Certain devices terminate and re-initialize the audio path within the unit however,
they pass the video untouched. This creates different path lengths for the video and
audio. This difference in path length creates different peak and boost levels for audio
and video. When audio-breakaway is implemented, the audio and video paths are
likely to be different.
Compensation
Twisted pair cables experience a loss of bandwidth and signal strength over distance.
When the loss is within certain limits, the reduced signal can be restored through
peak and boost compensation adjustments. The amount of compensation required is
directly dependent on the length of the cable. Therefore, each device in a network
requires a specific amount of compensation.
Manual Compensation
In a manual compensation system, the compensation parameters, along with
microphone equalization settings, are stored in the receiver in a preset file. When the
program switches to a new transmitter, the program recalls the compensation settings
associated with the new transmitter. In large systems containing multiple transmitters
and receivers, these parameters must be stored in multiple locations, creating a
complex arrangement.
Auto Compensation
In a system utilizing auto compensation, the peak and boost values are stored in a
preset file at the receiver. The transmitter stores the input compensation and
microphone EQ settings. When the program switches to a new transmitter, the
transmitter ID, input compensation and microphone EQ settings are sent over the
audio channel of the QM cable to the receiver. The receiver is equipped with a hunt
algorithm to search for the proper peak and boost settings. Once the receiver acquires
a QM Link signal, it can receive the audio signal containing the transmitter ID, input
compensation and microphone EQ settings. After receiving the transmitter ID, the
receiver recalls the peak and boost preset and uses these values to properly adjust the
video signal.
NOTE: If auto compensation is used in your QM system, all QM devices must use
it. If it is not used in your QM system, it must not be used for any of the QM devices.
38 • QuickMedia™ FlipTop Computer Center: QM-FTCC Operations & Installation Guide – DOC. 6313B