19
3
AVB Networking Basics
3.3
Choosing the Right Cables
StudioLive™ Series III
AVB Networking Guide
3.3.4
Plug Termination
Making your own Ethernet cables can be a great way to save money, and
allows you to create cables to fit your needs and specifications exactly. If
you choose to make your own Ethernet cables, it’s important to be aware of
some possible pitfalls and follow some important general guidelines.
Most RJ-45 connectors are designed to be used with either solid-core or stranded
cable; however, you should always confirm the connector’s compatibility
to the type of cable you are deploying. Using a plug designed for one type
of cable with the wrong cable type can produce unreliable results.
The same is true for CAT5e and CAT6 cable connectors. Most RJ-45
connections are only meant to be used specifically with one or the
other. Additionally, some connectors are designed for specific wire
gauges and cable diameters, so, again, you should always confirm your
connector’s compatibility with the specific cable you are using.
Power User Tip:
Just like sourcing cable, it’s important to source quality connector from a
reputable vendor. The connector itself is one of the most crucial pieces in the equation.
Even the highest quality cable is only as good as the connections terminating each end.
3.3.5
T568A or T568B
There are two wiring pinouts defined by TIA/EIA standards: T568A and T568B.
Currently, T568B is used almost universally in the U.S. - a legacy of analog telephone
compatibility - while T568A is more common worldwide. Either is perfectly
acceptable as long as you are consistent. If you’re doing a new wiring install, it’s
best to choose one or the other and stick with it throughout your network. If
you’re making new cabling and not sure about an existing wiring install, don’t
worry, it’s even okay to intermingle the two standards for the most part. The most
important consideration and the only rule you absolutely must follow is that for
a given cable or run,
you must use the same wiring standard on both ends
.
3.3.6
Twisted Pair Tips
When building your own twisted-pair Ethernet cable, it is crucial that
the twists are maintained as close as possible to the contact termination
within the plug as possible. You’ll also want to make sure that the wire pairs
running to adjacent pins are parallel inside the plug body all the way to
the pin. You don’t want different pairs wrapped around each other or have
wires bunched up inside the plug and pressed against each other.
Trimming the wire pairs to the proper length is also crucial, as you
want to make sure that the back-crimp of the plug is clamping
down on the cable jacket, not the wires themselves.
You might be surprised at how easy it is to create a poor termination and how
narrow the window is between a working cable and a failing cable. The crosstalk
performance and EMI rejection capabilities of Ethernet cable, which ensure it will
function up to its rated specification, are entirely dependent on maintaining these
relationships of the wires within the cable and the plug termination. A little attention
to detail goes a long way in this respect. Again, if you are unfamiliar with proper
termination techniques, PreSonus recommends consulting with a professional.
