NXU-2B Operations Manual
2-7
Interoperability Now!
2.8.2.1
Audio Input
The NXU-2B audio input is 47K ohm, balanced. It can be used as an unbalanced input by
grounding one half of the balanced pair and connecting the single-ended input to the remaining
half. Balanced inputs and shielded cables are recommended for superior noise immunity.
The audio input will accept signal levels from –26 to +10 dBm. Internal circuitry is used to
amplify or attenuate this input as necessary to optimize the level to the DSP. The signal level is
adjusted by the “RX input level” pulldown in the web interface Configuration page. The input
is set to 0 dBm when shipped. This mean an audio input level of 0 dBm is expected and provides
the correct level to the internal audio circuitry.
2.8.2.2
Audio Output
The audio output from the NXU-2B is a balanced 600-ohm output. The output level is adjusted
by the” TX output level” pulldown in the web interface Configuration page. This output provides
a 0 dBm nominal level into a 600-ohm load. The TX audio output will supply signal levels from
–26 to +10 dBm.
2.8.2.3
COR Input
The COR input to the NXU-2B is a high impedance input and can be programmed to be active
high or active low. In the active low configuration, the input is pulled up to +5V DC internally
through a 47K ohm resistor. In the active high configuration, the input is pulled down to ground
through a 22K ohm resistor. The logic threshold is 2.5V DC nominal, and the input is protected
from momentary surges up to +100 V DC.
2.8.2.4
AUX Inputs
The AUX inputs (AUX IN0 and AUX IN1) are high impedance inputs and are always active
low. They are pulled up to +5V DC internally through a 47K ohm resistor. The logic threshold
is 2.5V DC nominal, and the input is protected from momentary surges up to +100 V DC.
2.8.2.5
PTT Output
The NXU-2B’s default PTT output is a “ground” through an E&M Relay. Additional options
allow (See Section 2.5):
o
That the E&M Relay Return be a pin on the Audio/Control connector.
o
That an open drain transistor pulled low be used instead of the relay. This transistor can
sink up to 100 mA of current and can withstand open-circuit voltages up to +60V DC.
In order to avoid conflicts with internal pull-up resistors on the PTT lines of some radio
equipment, there is no internal pull-up resistor on the NXU-2B PTT output.
2.8.2.6
AUX Outputs
The AUX outputs from the NXU-2B (AUX OUT0 and AUX OUT1) are open drain types. They
can sink up to 100 mA of current and can withstand open-circuit voltages up to +60V DC. These
lines are pulled up to +5V DC through a 47K ohm resistor.
Summary of Contents for NXU-2B
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