7700 MultiFrame Manual
7707IT Multi-Channel Intercom Fiber Transceiver
Revision 1.7
Page - 21
4.2.6. Setting the Analog Audio Detection Threshold
In order to properly indicate audio signal presence, a detection threshold is used. The audio detection
threshold adjustment is implemented in the digital domain. For matrix type intercom signals the specified
range of threshold adjustment is –30dBu to +10dBu, in 1dB increments. For party-line type intercom
signals the specified range of threshold adjustment is –40dBu to 0dBu, in 1dB increments. Threshold
adjustment is done using the card-edge interface or through
Vista
LINK
®
control.
The audio detection threshold is independently adjustable for each channel, and is applied to both the
input and output of each respective channel. The detection thresholds are applied to the audio signals at
the input and output connections, which may have gain applied. Refer to section 4.2.3 for information on
how to display the audio signal presence on the card-edge LEDs.
CTRL
To change the audio detection threshold, select the
CTRL
menu item in
menu level 1. The 7707IT allows an audio detection threshold to be set for
each channel. Use the toggle switch to choose the channel for which you
want to adjust the detection threshold. Press the pushbutton to apply the
displayed selection.
CH01
to
CH08:
Range of channels for the 7707IT-8.
CH01
to
CH03:
Range of channels for the 7707IT-3.
Use the toggle switch to select the
DET
menu item and press the
pushbutton. The toggle switch may then be used to change the threshold
value. Use the toggle switch to select the desired value then press the
pushbutton to apply the displayed selection and return to menu level 3. You
can select other items on menu level 3, or select the
BACK
menu item to
return to menu level 2.
-30
to
+10:
Detection threshold range for matrix intercom types,
describing a dBu value.
-40
to
0:
Detection threshold range for party-line intercom
types, describing a dBu value.
The factory default configuration applies the following audio detection
threshold values:
-
+8
for the TXMX (RTS-Telex Matrix) profile
-
0
for the CCMX (ClearCom Matrix) profile
-
0
for the TXPL (RTS-Telex Party-line) profile
-
-8
for the CCPL (ClearCom Party-line) profile
Changing the interface profile will restore the factory default threshold value
for the respective channel(s).
CH01 to CH03 or
CH08
DET
-30 to +10
-40 to 0
4.2.7. Setting the Audio Gain
Audio gain adjustment is implemented in the digital domain. For matrix type intercom signals the
specified range of gain adjustment is -10dBu to +10dBu, in 0.1dB increments. For party-line type
intercom signals the specified range of gain adjustment is -5dBu to +5dBu, in 0.1dB increments. Gain
adjustment is done using the card-edge interface or through
Vista
LINK
®
control.
