NXU-2B Operations Manual
3-14
3.4.12
VOX Hang Time
When VOX mode is enabled, you may also adjust the VOX hang time. This is the amount of
time the VOX remains active after the input signal falls below the VOX threshold, and may be
set to 500, 1000, 2000, 3000, or 4000 milliseconds. This is useful to prevent the VOX from
dropping out between words or syllables. Use the HANGTM command followed by 500, 1000,
2000, 3000, or 4000 to select the hang time. The factory default is 500 milliseconds.
3.4.13
COR Inhibit Time
In some applications it may be necessary to inhibit the NXU-2B’s response to the COR input
(whether hardwired COR or VOX) for a brief period of time (and under certain circumstances)
in order to avoid problems with the “ping pong” effect.
The “ping-pong” effect can occur when the COR output of a device is activated momentarily by
the device when it switches out of the TX mode. There are varieties of reasons why this can
happen (including squelch tails on some radios), and it may occur with COR or VOX, but the
result is the same.
To illustrate the problem, assume that there are two radios connected over a network by a pair of
NXU-2Bs. An active COR at one end of the network creates an active PTT at the other end.
When the COR of Radio 1 is active, Radio 2 is transmitting, and vice versa. Consider what can
happen when the switch out of the TX mode causes a momentary active COR output:
Radio 1 COR becomes deactivated, so the Radio 2 switches out of the TX mode and
activates its COR output momentarily. This momentary Radio 2 active COR signal
causes Radio 1 to switch momentarily to TX mode, and when it quickly drops back out
of the TX mode its own COR output is momentarily activated. This will once again put
Radio 2 in the TX mode, causing an endlessly repeated cycle where the radios “ping-
pong” back and forth and in and out the TX mode.
The COR Inhibit feature prevents this problem by ignoring any active COR input that occurs just
after the NXU’s TX output command is de-activated. The unit ignores the COR input (whether
hardwired or VOX) only in the specified interval immediately following the inactivation of its
PTT output. Use the CORINH command followed by 500, 1000, 2000, 3000, or 4000 to select
the COR inhibit time in milliseconds. Type CORINH 0 to disable the COR inhibit feature. The
COR inhibit time should be set as long as required to prevent the “ping-pong effect”, but no
longer, or the beginning of a valid audio signal being transferred might be lost.
3.4.14
Voice Compression Settings
In order to send voice information over an IP network efficiently the NXU-2B uses digital signal
processing algorithms to compress the voice information so that it requires less network
bandwidth. The NXU-2B offers several different voice compression methods 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:
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