Misunderstanding of wiring test system

Since the end of 1995 to release the Test standard TSB-67 has been nearly three years, but some of the domestic wiring construction units in the project acceptance test, there are still some non-standard behavior.
Near-end crosstalk (NEXT) test problem
The most common problem is that the measurement of near-end Crosstalk (NEXT) is not tested at both ends according to the specification, especially when the link is over 40 meters. Because the attenuation of the signal in the link makes the next signal produced at the far end unable to be measured by the instrument on the Test side, it is easy to assume that the link is normal. A problem with a disconnected connection can only be found after the network device is connected. To avoid this error, the next value must be measured at both ends of the link. The use of two-way tester although the initial investment is large, but in the future long-term testing process will save time and manpower can definitely offset this investment.
Short link problem.
When a link is shorter than 15 meters, because the link attenuation is too small, the next value measured at the test end may be the cumulative value of the remote next, so when the next value is too large on the short link, it must be measured at the other end. In fact, when using a tester to measure jump wiring, other test items are of little significance except for wiring diagrams.
155MHz Test Frequency problem
Because ATM uses NRZ encoding to transmit digital signals, its data transfer rate is 155Mbps, but the bandwidth required is only 67MHz. Therefore, in the five-class wiring system used in the 100MHZ test frequency verified wiring system can run ATM network absolutely. Many users mistakenly believe that Mbps and MHz are the same unit, and some tester manufacturers are using 155MHZ testing frequency for commercial purposes to lure users into acquiring such instruments. In fact, the test specifications used by this type of instrument in the test frequency exceeding 100MHz are all made by the manufacturer itself, because the highest test frequency specified by TIA and ISO for the five types of cables is 100MHz, and the six type cable is 250MHz, so the test frequency above 155MHz is not standard. , it is meaningless. (Computer science)
Test standard of shielded cable
Shielding cable than unshielded cable more than one shielding layer, so many users would rather spend more money to buy shielded cable. However, if the construction of the shielding layer did not do the right grounding treatment, it can not only play the role of shielding, but will make the shielding layer into the source of interference signals. At present, TIA only has a standard for unshielded cables, so users should be able to use unshielded wires with ease. The biggest advantage of unshielded cable is that it is cheap and easy to construct. You will be able to master the quality of wiring engineering construction by verifying the wiring system with the tester.
Must have the concept of "with the load to be tested"
When a link is completed, the tester must be tested immediately and not after all the links have been completed. The basic link specification on the instrument is the specification used by the construction unit in the test, while the channel specification is the specification used when the customer carries on the whole wiring system acceptance.
Save the test results
The test results must be numbered and stored. In order to protect the rights and interests of users, the test report provided by the tester should be a computer text file that cannot be modified, it must be a computer file that is encrypted and cannot be modified by the construction personnel.
The problem of gigabit network and five kinds of lines
"It is wrong to say that a five-class cabling system must be used to run Gigabit Ethernet." IEEE (International Institute of Electrical and Electrical engineering) has negotiated with TIA that the gigabit network can still run on the current five-class cabling system. In order to ensure that the original 5 wiring system can successfully run gigabit network, as long as the wiring system with new test parameters can be again. In the Gigabit network test, the test frequency is still 100MHz, still within the range of five types of system bandwidth allowed. However, in the new network system, the author recommends that users try to use the new Cat 6 or cat 5E cabling products.