Visara iCON-XT Installation - Manual (Page 22)

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ICON-XT Server - Installation and Maintenance Manual
Twisted pair cabling systems can use both Unshielded Twisted Pair (UTP) and
Shielded Twisted Pair (STP) wires, but they must provide a100 ohm impedance.
Since the twisted pair cabling system is unbalanced and the Twinax interface on
the host processor and the STA or QTA in the ICON server are balanced, an
impedance mismatch occurs. The twisted pair cabling system cannot be attached
directly to the Twinax interfaces.
The Twinax interfaces are attached to the twisted pair cabling system by use of a
matching transformer. The matching transformers are called baluns, which is an
acronym for balance unbalance. Twinax baluns are available from a number of
commercial sources.
The following are generally accepted rules for using baluns and twisted pair cabling
systems to attach the ICON servers to the host processor.
1. Baluns are to be used for point to point connection.
a. They are not to be daisy-chained.
b. It is recommended that, if used, baluns should provide the interface from
the host processor to the first device in the chain, and true Twinax be used
for connections from the first device to the rest of the chain.
2. Balun pin outs must match end to end.
a. It is highly recommended that baluns be used in “matching” pairs, i.e.,
from the same vendor and same part number.
3. Baluns are available in RJ11 and RJ45 configurations. They cannot be mixed
on a single run of twisted pair.
4. When providing multiple connections through a twisted pair cable bundle, it
is recommended that not more than 70% of the pairs be used for signal
conductors.
5. Do not reverse the Twinax phase A and Twinax phase B signal between baluns.
a. Be sure the wire color continuity is maintained between the baluns.
6. The twisted wire used for this installation should minimally be;
a. AWG No. 24 or larger, solid copper twisted pair.
b. Maximum D.C. resistance not to exceed 94 ohms per 1000 meters.
c. Impedance range of 90 to 120 ohms at 256 kHz.
7. Assuming the twisted wire is AWG 24, the maximum safe total length of cable
providing acceptable signal integrity is 1600 feet (488 meters).
a. With ideal conditions and an EMI quiet environment, runs to 2000 feet
can be used.
b. Twisted wiring cabling systems do not provide the same level of EMI
isolation as provided by the Twinax cabling system.
c. If the environment that the twisted pair cabling system is being installed in
has an active and busy existing cabling infrastructure, the maximum safe
total length of cable providing acceptable signal integrity should be reduced
by 20% to 1300 feet.
d. Wire sizes smaller than AWG 24 will reduce the maximum safe total length.
e. Each interconnect (connection) on the twisted pair run adds a certain
amount of signal loss. To offset this loss, reduce the maximum safe total
length by approximately 16 feet per interconnect.