53
CHAPTER 6: Cable Test Descriptions
6.6.2 V
IEWING
N
OISE
R
ESULTS
The display provides a continuously updated, real-time report illustrated by
the following figure:
NOTE
When testing a 10BASE-T cable per the IEEE 802.3 specification, the
maximum allowable impulse-noise rate is 0.2 impulses per second with a
260-mV noise threshold.
6.7 Pair Reversal Test
The Pair Reversal Test provides a means to verify the NEXT measurement
consistency of the SCAN-LAN Vt as recommended by the draft TIA TSB-67
Link Testing Standard. In the Pair Reversal Test, the NEXT of a link is first
measured when transmitting on one pair and receiving on another. Then
the test is performed again with the transmit and receive pairs reversed.
The results should agree within the magnitude of the SCAN-LAN Vt’s
NEXT measurement-accuracy specification. The test is performed
automatically on all pair combinations.
F1
F2
F3
F4