NXU-2B Operations Manual
3-5
Interoperability Now!
3.3.9
Voice Compression
In order to send voice information over an IP network efficiently the NXU-2B uses digital signal
processing algorithms to compress the voice information. Several different voice compression
methods are available to support a variety of applications. For example, some compression
methods work well with voice and provide a high amount of compression, but do not handle
signaling tones very well. Other methods handle tones and voice but use more network bandwidth
because they offer less compression. You may select the method from the following voice
compression schemes that optimizes the trade-offs for your particular application:
1. GSM 13Kbps - Suitable for voice communications only. Should not be used if any tone
signaling is required. Offers the greatest compression with reasonable voice quality.
2. ADPCM 16Kbps – Suitable for voice or tone signaling. Offers good voice compression, but
the voice quality is lower than the other compression methods.
3. ADPCM 24Kbps – Suitable for voice or tone signaling. Offers less compression than ADPCM
16Kbps but the voice quality is higher.
4. ADPCM 32Kbps – Suitable for voice or tone signaling. Offers still less compression, but the
voice quality is the best of the ADPCM compression types.
5. PCM 64Kbps – Suitable for voice or tone signaling. Offers the highest audio quality of all
compression methods but provides the least compression. This is the default setting.
3.3.10
VoIP QOS DSCP Value
QOS stands for Quality of Service; some networks allow prioritization of some classes of
network traffic over other classes – for example, establishing a higher QOS for VoIP packets,
which have higher susceptibility to problems if there is significant jitter. High priority traffic can
be given “best effort” for delivery. The classification (differentiation) is done by DSCP value.
DSCP stands for Differentiated Services Code Point, and consists of a packet header value
between 0 and 63.
Again, unless QOS is supported on the network that the NXU-2B resides on, this setting will
have no effect.
3.3.11
Serial Port Settings
Baud Rate options are 300, 1200, 2400, 4800, 9600, 19200, 38400, 57600, and 115200. The
number of data bits may be set to either 7 or 8 using the DATA command, and the number of
stop bits may be set to 1 or 2. The serial port parity options are odd, even, or none.
3.3.12
COR Sense (COR/VOX/VMR)
The NXU-2B has several methods to determine when to send audio data across the network. This
is an important determination, because if the NXU-2B is connected to another NXU-2B/radio
pair, that remote radio will be placed into TX mode and retransmit that audio.
There are several options for determining valid audio. Use of a COR signal direct from the radio
(sometimes called
Hardware Cor)
is best, but this signal is not available on all radios; plus
Summary of Contents for NXU-2B
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