General Wiring FAQ and test method

PDS (Premiseadistributionsystem) is widely used in modern architecture, and is based on the development of computer technology and communication technology to further adapt to the needs of social information and economic globalization, office automation, commercial networking, The result of further development of marketing electronics is the combination of building technology and information technology.

The integrated wiring system is often divided into "one, two, three systems".

namely equipment, work area, management zone, horizontal wiring subsystem, trunk subsystem and complex backbone subsystem. Drawings for the integrated wiring system schematic diagram.

Integrated wiring technology in China has been accepted by the majority of IT industry, in the actual wiring construction, testing and acceptance process, due to the wiring engineering integration of the project organization capacity, project implementation capacity and project management capacity differences, integrated wiring engineering quality are different. In the second half of 1997, the Ministry of Telecommunications Products Quality Supervision Center for the comprehensive wiring Project acceptance test, half of the project quality problems exist in the integrated wiring market there are many urgent problems to be solved. ---http://bianceng.cn (computer science)

Standard for cable certification testing
Today all networks are defined to support five types of twisted pair, users need to determine whether the cable system to meet the five types of twisted-pair specifications, in order to meet user needs, the EIA (American Electronics Association) has developed the EIA586 and TSB 167 standard, which is used for the installed twisted pair network, provides a "certified" Whether the twisted pair is up to the standard of five line requirements. The TIA568 standard defines the specification of cabling and connection hardware in UTP (unshielded twisted pair) cabling and does not prescribe five types of twisted pair (UTP5 or STP5) that are installed on site; The TSB 167 standard contains all the specifications defined by the validation TIA568 standard, The UTP Link test is further standardized, it is a tia568a standard, applicable to the on-site installation of the five types of twisted pair of wire certification standards.

The main content of the TSB 167 test: ① Wiring diagram (Wire map): To confirm the alignment of the chain route cable to the correctness, to prevent crosstalk. ② link Length: For each link length is recorded in the management system, the length exceeds the target, then the signal loss is larger. ③ attenuation: It is related to the length of the cable and the frequency of the transmission signal. As the length increases, the attenuation of the signal increases, and the attenuation varies with the frequency, so the attenuation of all frequencies in the application range should be measured. ④ near-end crosstalk: Is the measurement of a UTP link from a pair of lines to the other line of the signal coupling, is the cable performance evaluation of the most important indicators, is the transmission and reception at the same time the interference signal. ⑤ DC Loop resistor It is a pair of wire resistors and the IS011801 regulation shall not be greater than 19. 2 Ω. ⑥ characteristic impedance: including the resistance and frequency 1~100mhz between the inductance and tolerance, it and the distance between a pair of wires and the electrical characteristics of the insulator.

Cable testing can generally be divided into two parts of the cable verification test and cable certification test. The verification test of the cable is to test the basic installation of the cable, the circuit breaker, short circuit, length and the connection of the twisted pair of the cables are generally tested. Verify that the test does not test the electrical specifications of the cable. Certification testing, refers to the cable in addition to the correct connection, but also to meet the relevant standards, that is, the installation of cable electrical parameters to meet the requirements of the required indicators. It includes all the contents of the verification test and the standard test cable's index such as attenuation, characteristic impedance and so on. Verification tests do not guarantee that the installed cable can pass through high-speed network digital signals, such as 100MHz. Only through the certification test can the installed cable be able to support the 100MHz signal. At present, many users of the installation of twisted-pair cable does not carry out certification testing, but in the network debugging process for testing, when the network can be connected to the thought that the installed cable is qualified. This practice is not only wrong but also very dangerous. Network debugging can be connected does not mean that the cable meets the installation criteria, nor does it mean that the cable works correctly when the network is running properly. In addition, the majority of users are currently installed five types of twisted pair, running the network is 10BASE-T, but 10base-t can run does not mean that 100BASE-TX can also run. Therefore, the installation of the cable can support high-speed signal must pass the relevant certification test to prove its performance, otherwise, when the upgrade to the high-speed network only to find the cable problem, at this time it is difficult to repair.

Select UTP (unshielded twisted pair) cable and STP (shielded twisted pair) cable shielding system is to ensure the system in the electromagnetic interference environment transmission performance, this interference includes external electromagnetic interference and the system itself signal transmission of electromagnetic radiation. In fact, the use of shielded twisted pair or unshielded twisted pair is largely dependent on the consumption concept of the wiring market. In Europe, the mainstream shielding system, in North America, the implementation of unshielded wiring system. No matter what kind of system, as long as the standard through the perfect design and installation, can achieve the desired effect. Only the price, installation difficult requirements are different.

For shielded twisted-pair wire, a single layer of metal shielding is not enough, more importantly, the shielding layer is completely grounded, so that the interference current can effectively guide the earth. In the actual construction, the use of shielded twisted-pair wiring system can achieve 360° full shield is very difficult, if the shielding grounding is poor, it will lead to its performance rather than unshielded twisted pair.

For unshielded twisted pair, in the non shielded channel of signal transmission, the external electromagnetic interference received in the transmission is simultaneously loaded on the two conductors of a pair of cables, and the two voltages of equal phase are formed. To the receiving end, cancel each other to achieve the purpose of eliminating electromagnetic interference. A pair of twisted pair is directly proportional to the external electromagnetic interference, and it is easier to operate than the shielded twisted pair in construction, and has a unified certification standard. UTP (unshielded twisted pair) is a reliable and mature wiring technology, which can meet the requirements of the jamming environment under normal circumstances. If the environment interference is big, one can use the metal bridge and the pipeline to do the shielding layer wiring method, another kind may use the optical cable to replace the unshielded twisted pair line to achieve the anti-interference purpose.

Determine cable link (link) and cable channel (Channel)
The previous LAN mainly used thin cable or three types of twisted pair, due to the increase in network speed, users are now a large number of five categories, super five twisted pair. According to what criteria can be certified user installed UTP5 line reached 100MHz indicators, can support high-speed network? TSB-67 for the installation of UTP5 line and on-site testing set specific methods and indicators, TSB-67 standard for a large number of horizontal connections are defined, it divides the cable connection into basic links (Basiclink) and channel (Channel). Basic link refers to the fixed cable part of the building, which does not contain a connection cable to the end of the network device, and the channel (Channel) refers to the entire connection between the network device and the network device, and the two connections are applicable in different scopes. Basic link is suitable for cable installation company, its purpose is to carry on the authentication test to the cable that installs, Channel is suitable for network user, because they care about the overall performance of the network, so should the entire cable part (Channel) between network equipment authenticate test. In particular, the link is not equal to the cable, the cable is only a part of the link. If you want to install a cable system that can support 100MHz of bandwidth, it should be the link to achieve this capability rather than just the cable.

Super five type twisted pair and super five link
Super Five twisted pair cable is a pair of cable manufacturers recently introduced for the local area network of twisted pairs. These manufacturers claim that the Super five line can support the 300MHZ signal transmission frequency. In practice, the above index is not reached at all, the highest transmission frequency of the current LAN is not more than 100MHz. 100base-tx This relatively new Fast Ethernet also has no more than 100MHz transmission frequency, so in the near future has not seen its actual application where the cable is different from the link, the cable can reach 300MHz transmission frequency, but not equal to the link can reach such a high frequency. Because the link is composed of cable, plug, socket and even coupler, wiring frame. If you want to get a five-class link, you must ensure that all components in the link are up to five standards. It doesn't make sense to have a cable that's super five and the link doesn't reach the Super Five category. At present, there is no way to carry out the authentication test on the Super five type link of the installation, that is, there is no standard to test the actual performance of these high-speed cable in the field at present, and can not guarantee the actual investment at all.

Generation and measurement of crosstalk
In a twisted pair, when the signal is transmitted on a pair of cables, it also generates an inductive signal in the adjacent line pair, that is, the signal is received by another adjacent line pair when the two lines send a signal, and this phenomenon is crosstalk. Crosstalk is divided into near-end crosstalk (nearendcrosstalk) and distal crosstalk (fafendcrosstalk). Near-end Crosstalk is the crosstalk that occurs at the transmitter end, and the distal crosstalk is the crosstalk at the receiving end. The influence of the signal transmission is the near-end Crosstalk, the near-end crosstalk loss and the signal frequency and the length of the channel and the construction technology.

Near-end crosstalk loss measurement, should include each cable channel at both ends of the device connectors and work area cable, near-end crosstalk does not represent the crosstalk generated at the near end, only to indicate the value measured at the near end. The measured values vary with the length of the cable, and the longer the cable, the smaller the near-end crosstalk value. It is proved that the near-end crosstalk in 40m is real, and the near-end crosstalk loss should be measured separately from both ends of the channel, and now the tester has the ability to test the near end crosstalk at one end.

In the construction of integrated wiring, we should optimize cabling materials such as cables and information modules, employ senior professional construction units for design, hire professional firms to carry out comprehensive wiring certification tests, and check and accept the project according to the test report, and keep all the comprehensive wiring documents so as to better maintain the network system.