IBM 5500-01E, Руководство по эксплуатации, установке и обслуживанию

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example, between punch down blocks). Solid wire is used for the short patch
cables between patch panels or from the wall plug to the device.
Most RJ connectors accommodate wire gauges of 24 or 26 gauge, not 22
gauge. This limitation is based on the physical pin spacing standard of the
connectors. Although 22 gauge solid wire is often used between punch down
blocks (for reduced attenuation), it should not be used with RJ connectors
unless specifically approved by the manufacturer.
When attaching RJ plugs to UTP cable, always use plugs and crimpers that
are made or approved by the same manufacturer. Mixing the components
from different manufacturers can result in unreliable connections.
Patch Panels
When using twisted-pair cable, use a modular patching system. This system
allows you to quickly move, add, and change cables and gives you greater
flexibility for troubleshooting.
A patch panel using AT&T 110 or KRONE punch blocks is recommended
over the standard telephone M66 style punch block. The 110 and KRONE
blocks provide superior electrical connection and improve the line isolation
over the M66 block.
The following connectors are not recommended:
• Telco connector (RJ21), typically used with the M66, causes signal
attenuation.
• Multi-pair trunk cable (for example, 25-pair cable, 300-pair riser cable);
these cables exhibit poor signal crosstalk properties.
Balun Standards
Baluns physically convert media types while matching impedances and
providing isolation. During IBM midrange host communication, baluns
typically convert from a 93 ohm twinax cable to a 100 ohm unshielded-
twisted pair (UTP) cable. Baluns are also available to convert DB15
connectors (male or female) to UTP.
Baluns are available with either RJ11 or RJ45 modular connectors. Twinax
baluns use two wires (that is, 1 twisted pair) for data transmission. These two
wires can translate into different RJ connector pinouts and phases (normal or
reversed).
Note: The DB15 D-shell connector that is used for IBM 5250 Emulation
Family adapters has the following relationship between phase A and phase B:
Phase A is pin 7
Phase B is pin 14
The IBM normal and reversed phase designations are listed in Figure 75.