IBM 5500-01E, Operational, Installation, And Maintenance Manual

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all the devices on the port return to the standard 1 Mbps mode communication
rate.
For optimal performance, IBM recommends keeping your Express-enabled
devices on a separate port from your non-Express devices.
When planning for 2 Mbps mode, it is important to note that the maximum
support cable lengths are shorter than used with the standard twinax protocol.
For more information, see Figure 7 on page 33. If installed cables are too long
to support 2 Mbps mode, the WSC will operate at the standard 1 Mbps mode
rate.
Note: Not all UTP hubs or multiplexers support the Express data stream. The
IBM 7299 product family does support all functions of the Express data
stream and the Dual Mode function of the workstation controller.
Common Cable Problems and Associated Tests
This section describes some of the most common cable problems and the
common cable tests to isolate these problems. References to twinax cabling in
this section can refer to all three twinax cabling methods described in this
manual. Some common cable problems are:
• Power and grounding
• Wire resistance and attenuation
• Extraneous voltage on the signal wires
• Stubs, bridge taps, and extensions
• Wire characteristic impedance and impedance discontinuities
• Crosstalk
• Shorts, opens, and other wire faults
• Electromagnetic interference
Power Receptacle
Incorrectly wired or grounded power receptacles can be a safety hazard and
can contribute unacceptable levels of noise onto the network. In some cases,
the errors caused by incorrectly wired or grounded power receptacles are very
intermittent. If the AC voltage is not within acceptable limits, the attached
device can introduce errors onto the network or can fail to work.
Power Monitors
An OEM Power Disturbance Analyzer can be used to measure voltage sag,
surge, and impulse (including impulse duration) on single and three phase AC
supplies. With the appropriate plug-in module, it will also record DC voltages.
The output is numeric on a paper tape roll.