Chapter 7
Cable Testing Fundamentals
7-31
Headroom Errors
The Headroom number, reported in dB, characterizes the worst-case margin found
in a single cable run. A large number is desirable, since it indicates a strong signal
and little noise interference. The pass/fail limit for Headroom is the same as Power
Sum ACR.
Testing and Troubleshooting 10BASE-T Cabling
10BASE-T Ethernet systems use twisted pair cabling for transmission of network
data frames. Both the cable and connecting hardware must meet minimum
standards as specified in the IEEE 802.3 standard. The default settings for
10BASE-T network links in the LANTEK tester reflect these standards.
10BASE-T systems use the 1 and 2 pins for transmit and the 3 and 6 pins for
receive, as shown in Figure 7-5. The instrument passes or fails the Wire Map based
on this pin configuration. If your system does not use the IEEE 802.3 wiring
standard, a custom adapter is required to align nonstandard transmit and receive
pairs.
Figure 7-5: 10BASE-T Connector
Note: Other pairs may be wired, but 10BASE-T uses only the pairs shown.
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