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11
GE N ER AL I N T E RFACE S
Front Panel Indicator
The LED on the front panel is normally red to indicate that power is present on the unit.
Rear Panel Connections and Operation
Null Adjustment
LF Full-
From Mixer
Output
Band
Main Output
to TBU
From Mixer
Bandpass
Output
Telephone
Filter
Level
Output
Switch
Adjustment
Fig 11-3: RB-MM1 Rear Panel.
Stereo Inputs From Mixer Main Output
These inputs should contain the main mixer output which will be a feed of the programme
plus the audio that you want to remove by the mix-minus unit. Ideally, the input should
be presented at 0dB. The XLR 3 pin sockets used for the left and right channel inputs are
electronically balanced and have an impedance of greater than 10kΩ bridging. Each XLR has
the following connections:
Pin 1: Screen.
Pin 2: Phase.
Pin 3: Non-phase.
Input From Mixer Telephone Fader
This mono input should contain the audio that needs to be removed by the RB-MM1, usually
from the telephone/telco fader of a mixing console. Ideally, the input should be presented
at 0dB. The XLR 3 pin socket used for the mono channel input is electronically balanced and
has an impedance of greater than 20kΩ bridging. The XLR has the following connections:
Pin 1: Screen.
Pin 2: Phase.
Pin 3: Non-phase.
Output Null Adjustments (LF and Full-Band)
The 2 x null preset potentiometers are used to adjust the null between the input from the
telephone fader and the main stereo input. The telephone input is made anti-phase and
used to cancel out that signal in the main stereo signal. So, the nulls adjust the level of anti-
phase signal required to achieve the best mix-minus null.
65
Redbox User Handbook No 3
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