Visara iCON-XT Installation - Manual (Page 21)

Chapter 2. Chassis Description and Installation Instructions
707097-001 2-9
floor. Additionally, the ICON XT can have up to five of the QTA cards installed,
(providing 20 Twinax connections) which would present a difficult cabling situation
on the rear of the machine if shorter standard “T” cables were used.
The standard “T” cable and the QTA T-cable terminate in the traditional dual Twinax
connector at the end that connects to the host (or site) Twinax cabling system. The
dual connector used on the cables is self-terminating.
There are two types of cabling systems used to attach the ICON servers Twinax
interface to the host processor; Twinax cabling and type five cabling with baluns.
Twinax cable system
The following are generally accepted rules for using Twinax cables to attach the
ICON servers to the host processor.
1. The maximum length for a single run of Twinax cable is 1525 meters
(5000 feet).
2. The ICON server can be connected at any point (distance) on the single
run of Twinax as long as the total number of cable junctions does not
exceed the maximum limit.
3. The maximum number of cable junctions in a single run of Twinax cable
is eleven.
4. A cable junction is defined as follows;
a. When the Twinax cable system attaches to an individual “T” cable at the
ICON server.
i. Although the “T” cable allows two connections, it is considered one
junction.
ii. If the “T” cable connection is the last connection on a single Twinax
run, it will not have a cable connected to one of its connectors.
b. When two sections of Twinax are joined using an industry standard cable-
to-cable adapter.
c. The “T” cables supplied with the ICON servers are self terminating.
i. If the ICON server is not the last device attached to the Twinax cable
run, make sure the last device provides termination.
ii. It may be necessary to use an external cable terminator is the last device
on the Twinax run does not provide self termination.
d. Twinax cable runs should not be installed near power lines transmitting
more than 440 volts.
e. Twinax cable runs should not be installed near equipment operating on
440 volts or more.
Twisted Pair Cable System
Many processor installations use twisted pair wiring to eliminate the high cost of
Twinax cable. Although twisted pair systems work well, there are some cautions to
be observed. As stated above, Twinax is a balanced line system where the two
internal conductors have equal signals (currents) flowing in opposite directions.
Twisted pair cabling is not a balanced line system and uses one conductor for the
signal (current) and the current in it returns to the source through a common ground.