7700 MultiFrame Manual
7707IT Multi-Channel Intercom Fiber Transceiver
Page - 22
Revision 1.7
Matrix audio types use a balanced voltage output signal. The selected gain value describes voltage gain,
and is accurate for high impedance loads. Analog audio output design dictates that the amplitude will
reduce slightly as the load impedance is reduced. Subtract approximately 1dB for 600
Ω
loads.
Party-line audio types use an unbalanced current output signal. This current output signal produces a
voltage signal across an external termination which is normally 200
Ω
. The termination is shared by all
connected intercom devices, and usually resides within the power source of the system. The selected
gain value describes voltage gain, and is accurate for a 200
Ω
termination. Other termination values will
yield a different gain as per the current-resistance product of the signal.
CTRL
To change the audio gain, select the
CTRL
menu item in menu level 1. The
7707IT allows independent configuration of each channel. Use the toggle
switch to choose the channel for which the audio gain will be adjusted and
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 audio gain
value. Toggle to 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.
-10
to
+10:
Gain range for matrix intercom types, describing a dB
value.
–5.0
to
+5.0:
Gain range for party-line intercom types, describing a
dB value.
The factory default audio gain setting is
0
dB. Changing the interface profile
will restore the factory default gain value for the respective channel(s).
CH01 to CH03 or
CH08
GAIN
-10 to +10
-5 to +5
4.2.8. Selecting the Serial Data Termination
To simplify installation, the 7707IT provides a selectable input termination of 110
Ω
for the balanced serial
data signals. This termination should be active as required by the specific application, and common
practice. Selection of the termination is done using the card-edge interface or through
Vista
LINK
®
control.
