NXU-2A Operations Manual
6-2 Interoperability Now
Where can I find a description of the VoIP protocol used by the NXU-2A?
The NXU-2A protocol is proprietary and not available to end-users without a license. Contact
JPS for further information.
My system uses pilot tones and/or tone keying. Does the NXU-2A support this?
Yes. Pilot tones and keying tones are not normally needed on the NXU-2A (due to its support
for hardware COR and PTT lines), but are supported and will work with the proper vocoder
selection. Tones are not supported when using the 13 Kbps vocoder (VOCODER 1). You must
use one of the higher bit-rate vocoders to use any type of tone signaling.
Can I hook one NXU-2A directly to another via their Ethernet ports?
Yes, if you use a crossover Ethernet patch cable. A straight-through patch cable (such as the
one supplied with the unit) can only be used to attach the NXU-2A to network interface
equipment such as hubs, switches, or routers. You can directly connect a pair of NXU-2A units
up to 100 meters apart using a CAT5 crossover cable. When directly connecting NXU-2A
units in this fashion you should set the subnet mask to 255.255.255.0 and the gateway IP
address to 0.0.0.0.
After losing power on one end of an NXU-2A link, it takes a while for the units to re-
establish communications. Why is this?
The NXU-2A will wait up to 20 seconds before determining that the link has been
disconnected. After that, it will attempt to close the IP connection, which may take several
seconds. Then it has to open a new connection. This process may take 30 to 45 seconds,
depending on your network.
What is the difference between a static IP address and a dynamic IP address?
On an IP network such as the Internet, the IP address is like a phone number. It is a unique
number that identifies the network device, and it allows connections to be made between
network devices. There are two kinds of IP addresses, those that are permanently assigned and
those that are assigned temporarily. Permanently assigned IP addresses are called static IP
addresses, while temporary IP addresses are called dynamic IP addresses. Static and dynamic
IP addresses work the same way, but a dynamic IP address is like having a telephone number
that nobody else knows; it effectively limits you to making outgoing calls only.
Why do we need static and dynamic IP addresses? Why not just assign addresses
permanently like phone numbers?
One problem with IP addresses is there are not enough to go around. There are "only" about 4
billion IP addresses available. On the surface that would appear to be enough, but some
companies use a lot of them, the military uses a lot of them, and all the millions and millions of
people using the Internet use a lot of them. To ease this problem, many Internet providers only
assign an IP address to a computer when someone actually dials in to connect to the Internet.
When they disconnect, the IP address goes back into the pool of addresses so someone else can
use it. This makes sense in cases where computers might sit for a long time without needing to
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