NXU-2 Operations Manual
6-5
JPS Communications, Inc.
through cable. If you wanted to connect two like devices (DTE to DTE or DCE to DCE) then
you needed a null modem (crossover) cable. The PC is a DTE device, and the NXU-2 and
ACU-1000 are DCE devices. That is why you need a crossover cable for connecting an ACU-
1000 to an NXU-2.
Can I change the vocoder on the NXU-2?
Yes. This is the voice compression method used to convert the audio signal into a digital
format. There are times when the user may want or need higher voice quality or transparency to
certain kinds of signaling tones. The VOCODER command allows the selection of different
vocoders, albeit at the expense of network bandwidth.
Can I pass modem tones over the voice port of the NXU-2?
Some types of modem tones (such as FSK) will work if you select one of the higher bit rate
vocoders, such as VOCODER 4 or VOCODER 5. Complex modem waveforms (such as 56K
modem data) will not pass. Pilot tone, keying tones, and other similar signaling tones will work
properly. In general the RS-232 port should be used to send data, however.
I've connected my radio to the NXU-2, I have the levels turned all the way up and can still
barely hear the audio. What's wrong?
The NXU-2 uses balanced audio on the input. If, instead of connecting to both balanced input
lines, you connect your audio to one audio input and ground, you'll get the effect described
above. There is enough leakage in the transformer to get some audio through, but it won't work
properly.
I've connected my radio to the NXU-2 and it works, but the audio sounds very "tinny" and
doesn't have much bass.
Make sure you haven't used the discriminator output, which is sometimes available on FM
receivers and transceivers. Discriminator audio is pre-emphasized, and there is no de-emphasis
circuitry in the NXU-2. You'll need to use your regular audio output instead.
I've connected the NXU-2 to my computer serial port as described in Section 3.3 of the NXU-
2 manual, but I can't put the NXU-2 into Command Mode as described in 3.3.1. What do I
do now?
First, if you're using HyperTerminal (the serial terminal program included with Windows) you
need to make sure that you have the flow control set to 'None' in the serial port configuration
menu. In addition, you may have to exit HyperTerminal and start the program again in order for
program configuration changes to take effect. Second, you must follow the instructions in 3.3.1
exactly. Wait 10 seconds and then type three plus signs +++ and nothing else. If you type more
than three plus signs the procedure won't work. Wait a few seconds and try again. In addition,
the three plus signs must be typed within a one second period in order to be recognized.
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