Hardware manual

Chapter 5 - Installing the CAB 4n
26 Version 1.6.0.0 March 15, 2010
The EIA standard requires no more than 1/2 inch be left untwisted. More than 1/2 inch of
untwisted cable will affect performance at high bit rates. Although only 2 of the 4 twisted
pairs are used for Ethernet, it is important that all pairs be terminated, and that the
conductors be twisted together in pairs. The illustrations should give you the basics for
getting your cables, and your audio system up and running. Although pre-made, molded
style cables are preferred, they are usually impractical, since your cabling route, distance and
locations are based on the jobsite conditions and not your test bench. Additionally, you will
need rack wiring, and bulk cable is the preferred way to dress off a wire harness.
Note: We recommend that you familiarize yourself with the wiring color schemes so they
are second nature to you. An error in the cabling of an audio network is often the primary
cause of system errors
Although the wiring standard used in CAT 5 cabling originates with AT&T, it is functionally
different for configuring Ethernet cabling. The Bell System uses a series of colors to identify
wire pairs. This color scheme identifies the pair numbers, and conductor polarity, and applies
to the wire, not the connector. It is important to know what pairs are which, and the function
of the pins on the RJ-45 connector. The colors are BLUE, ORANGE, GREEN and BROWN
for the first four pairs.
What is often confusing is that the pair numbers do not line up with the pin numbers on the
RJ-45 connector. In other words, conductor one of the cable (White w/Blue Strip) is not
terminated to pin one of the connector. The AT&T connecting standard always uses the
middle pins for the first pair. After that, they are staggered around, primarily to prevent
crosstalk between adjacent pairs. For Ethernet, only the ORANGE and GREEN pairs are
actually used.
Note: It is very important that you build the cable with all pairs properly terminated. This
will prevent any confusion later, and give your cable a solid mechanical connection.
For Ethernet, the BLUE and BROWN pairs are not used. The ORANGE pair is transmit
(TX), and the GREEN pair is receive (RX). There is a positive and negative conductor for
each pair, indicated by the color code. Notice on the chart that the order of the wire pairs
does not follow the connector pins. The first wire of a given pair is always the white wire
with a colored stripe and is the positive conductor. The corresponding colored wire with the
white stripe is the negative conductor for that pair.