In enterprise LAN, especially in some large-scale and complex LAN construction, generic cabling is a vital part of the whole network construction process, which is related to the success or failure of the whole network construction. Generally speaking, due to the complexity of network generic cabling, it is necessary to carry out detailed cabling system design first, and then carry out construction according to the design drawings and requirements. Only in this way can we have a definite aim, construct in strict accordance with the design requirements and meet the needs of users.

1、 Three main stages of generic cabling

Generic cabling in a large-scale building complex is a complex system engineering, which needs to be implemented step by step. The following is a brief description of several main stages of generic cabling project.

1. System design stage

The design of wiring system will have a decisive impact on the whole wiring process. Therefore, the designer should be careful, make sufficient investigation and research, and collect data related to corresponding buildings, such as architectural drawings, decoration drawings and other engineering data. If the building has wiring, data on the original wiring shall also be collected. Then fully consider the economic factors, application requirements, construction schedule requirements and other factors.

If the building is still under preparation, the requirements for generic cabling can be put forward, and specific requirements can be put forward for the design of the building according to the overall layout and wiring requirements, such as the channel specifications for wiring between floors up and down, embedding some pipelines, etc., which can provide convenience for generic cabling in the future. Some wiring work that can be carried out synchronously can be reflected in the building design drawing, so that some wiring can be completed in the preliminary project at the same time of construction, so as to avoid many disadvantages of later construction, reduce repeated labor, improve work efficiency and achieve reasonable and easy operation.

The situation of integrated wiring based on the original building is different from that of the interior decoration project. It must be redesigned according to the actual survey and mastering the data of the original building and the decoration design. Communication must be maintained between wiring design and decoration design, which provides convenience for the work of both sides.

In general design, material selection, equipment grade and layout are directly related to users' application needs and capital investment. If users are short of money, they can choose some moderate solutions. More attention should be paid to cost performance in the purchase of online materials and equipment. The distribution of information access points can also be relatively centralized, which can reduce the investment of wires and equipment and achieve the purpose of saving money. If the user is economically well-off and has high requirements for wiring, he can choose wires and equipment with higher performance, and the information access points shall be evenly distributed and appropriately advanced as far as possible for future expansion of the user.

2. Construction stage

In the specific generic cabling construction stage, many factors may be involved, including communication with users and construction and decoration construction units, as well as command on the construction site. At the same time, it is also necessary to master comprehensive standards and technologies, so the commanders must have high quality.

If the decoration and wiring construction are carried out at the same time, generally speaking, the wiring construction team is required to enter the site earlier and do a lot of preparatory work, such as trenching, drilling and laying pipelines on the wall. In order to take the initiative, the wiring construction unit should strive to start construction as soon as possible and carry out construction in a planned way. For example, it can first select typical places to do some tests to determine some details of specific construction, so as to provide experience and problem-solving methods for the full implementation of the following projects. The problems encountered shall be handled and solved as soon as possible. For the problems that cannot be solved at the moment, the designer can put forward corresponding supplementary and modification schemes according to the on-site construction conditions.

For example, in the construction of generic cabling project of a building, due to the late preliminary preparation, the lack of ideological preparation of decision-makers for the specific type of materials to be used, and the lack of experience of on-site commanders, the progress is very slow. At the same time, due to the lack of experience and technology, some technical problems can not be handled well, which makes the whole wiring project difficult. For another example, the partition walls of buildings are generally hollow bricks. If the method used is improper or the force is too large, it is likely to break the whole brick, which will not only make their own construction difficult, but also cause the dissatisfaction of the decoration Department, making the relationship between the two very uncoordinated. Due to the poor coordination between them, the wiring process can not keep up with the progress of decoration, and the contradiction between the two sides is likely to further intensify and affect the overall progress. Therefore, in this case, first of all, it is necessary to have a good relationship with the decoration construction team (including the following specific construction personnel) to make the project proceed in a coordinated atmosphere. Only in this way, many subsequent work can be coordinated and synchronized with each other.

In addition, during construction, the difficulties in pulling wire must be taken into account, and the pipeline with reasonable diameter shall be adopted. Especially in the case of many turns, the gap must be left as far as possible, and the work of the next step must be fully considered. Mark both ends of the stay wire and tie it in bundles according to certain methods to reduce the finishing work in the next step.

After the cables are laid in place, the next step can be carried out after other work (such as painting) of the decoration construction team is completed, such as making modules, upper panels, etc. If the module is installed before painting, some liquids such as lime water may be immersed in the module during painting, resulting in quality problems and rework. Similarly, in the morning, the panel will be dirty and increase the cleaning workload in the next step.

3. Inspection and acceptance stage

After the wiring work is completed, each information point shall be tested and checked. In general, fluke and other special instruments can be used for testing, one by one according to the marking diagram of each information point. If problems are found, records can be made first, and then individual problems can be checked after all the tests are completed. At the same time of testing, label the number of each point with label paper at the information point and distribution frame, and indicate it on the plan, so as to manage, use and maintain the system in the future. As shown in Figure 3-14, the equipment and wire in a cabinet are marked.

Generally, problems are found at both ends in the acceptance. This may be because the distribution frame is not done well, or the module is not done well. Another possibility is that the screws drill into the network cable when the upper board is used, resulting in short circuit, etc.

After all tests are completed, clean the plan and make a completely correct label drawing for future reference. At this time, it can be handed over to the user for acceptance. During the acceptance, due to the level and equipment, the user will generally require the construction party to provide test technicians and equipment. At this time, the construction party must provide them in full. Of course, because the wiring construction also has a warranty period (up to more than 10 years), the user's test and acceptance is only sampling inspection, which only requires the construction party to promise to solve the problems found during the actual network installation in time. Moreover, the test can not find all potential problems. The test is carried out in the real network environment when the specific application is fully launched. In addition, the whole construction drawing and label drawing shall be given to the user.

2、 Precautions for generic cabling

Generic cabling is a system engineering, in which the knowledge is very large. The following is the author's experience from the actual wiring project.

1. Wiring product brand specificity

The network products used in cabling, such as ordinary class 5 twisted pair or crystal head, transmit weak signals, and the slightest carelessness may affect the overall performance of network communication. Although there are some differences in performance and quality of wiring products produced by different manufacturers, for example, the quality of network cables produced by some manufacturers is better, the use effect of crystal heads produced by some manufacturers is better, and the network interface modules produced by some manufacturers are also good, the pen still suggests that wiring products of the same brand should be used in the same wiring system, Because this ensures compatibility to a large extent.

Many wiring people often simply believe that if those "good" network products are combined for wiring, the attenuation amplitude of network signal will be reduced to a small extent to achieve the communication effect. In fact, this understanding is incorrect, because the impedance of internal materials of network products from different manufacturers is different. Subtle differences in impedance may have a great impact on the signal attenuation of high-speed network, thus affecting the communication quality of the whole network system. Practice has proved that mixing the wiring of products from different manufacturers has little impact on the network switching with a speed of less than 10Mbps, but it will have a significant impact on the network system with a speed of 100Mbps or higher. Therefore, the network products produced by the same manufacturer are used for wiring.

2. Design reasonably before wiring and test strictly after wiring

This is a matter of work habits. The importance of good working habits can be better reflected in network wiring. Reasonable planning before wiring can greatly improve the efficiency of the network, otherwise it will seriously affect the efficiency of the network.

In the design stage, the needs of information system users are not fully considered, and sometimes the situation is very bad. For example, the cable trunk connecting the telephone and computer to the building can be guaranteed, but the connection of other building systems or equipment, such as fax machine, clock, safety and fire alarm system, elevator, property department system, etc., is often ignored. In order to avoid this situation, a detailed checklist of information systems and equipment can be prepared and provided to each department head before the system design, so that they can participate in the supplement. In this way, the above situation can be avoided.

But in fact, it is difficult to ensure that this situation will not happen again, because with the growth of user business and the change of business nature, the use needs of employees will also change. The office location of employees will be adjusted within or between departments, and the departments will also change the layout. The cable facilities designed should be able to cope with these conditions. A good way is to plan a general cable facility suitable for all equipment. Cables shall also be laid in unused space for future use, and the cable facilities in each workshop shall meet the needs of any user. For example, the setting of a workstation should not only meet the needs of financial personnel using a telephone and a PC connected to the local network, but also meet the needs of R & D personnel using telephone, modem, Internet accessible PC and shared printer.

After construction, in addition to testing whether the network is unblocked with the common ping command, some instantaneous burst high-throughput network switches are used for testing. Because the ping command only checks whether the network is connected. If the network traffic is very low, the problem is not big, but when the network traffic is very high, it may be difficult to surf the Internet.

3. Correctly understand the definition of 100m channel in the regulations

As we all know, the length of single network cable of category 5, super category 5 and category 6 lines shall not exceed 100m, which is stipulated in ANSI / EIA / tia-568 standard. But here we should correctly understand the meaning of 100m. According to the standard, this 100m should be the entire transmission channel of the horizontal section, that is, the management subsystem + horizontal subsystem + work area subsystem. Except for the 10m required for the cross connection of the management subsystem and the connecting cable of the work area, the actual large length of the embedded horizontal subsystem is usually only 90m, that is, the length of the basic transmission link.

It can also be simply understood that the entire transmission channel from the RJ-45 port of the work area network adapter to the nearby active connection equipment (switch, etc.) is 100m (including jumper).

4. Correctly select the communication cable wire of each part

In the actual generic cabling project, users often only pay attention to the computer network or current applications, but lack enough attention to some important but not obvious needs or future applications. If the pre built wiring cable structure in the building does not match the actual cable facilities, it will cause great construction delay and cost increase. Architects and electrical engineering companies are usually not familiar with the specifications and requirements of various wires, as well as the design parameters set by the American Electronics Industry Association and the American Telecommunications Industry Association (EIA / TIA) for cable structures in buildings, such as conduit, cable reel and equipment room. If the design does not meet the specifications, As a result, the existing threading pipe may not be able to accommodate all cables to be installed, so it is necessary to add threading pipe, or there are too many bending parts of threading pipe and no connection box, resulting in difficulty in cable threading, or the length of horizontal cable exceeds the requirements of class V wire due to the use of cable reel and connection box

3、 Integrated wiring grounding

When it comes to the grounding of generic cabling, many readers are confused. They will have the following questions: why is the twisted pair wiring not grounded? From this point, we can see that many users, even network managers, do not know the grounding in network wiring, and know nothing about its importance. In fact, this is determined by lack of work experience or limited responsibilities, because they have not conducted generic cabling at all. If so, they are only a single network cabling.

1. Grounding type of generic cabling

Because generic cabling is aimed at a whole building or even a group of buildings, its grounding is no longer a single ground wire problem, but includes multiple levels of grounding system. According to the regulations on grounding and wiring requirements of commercial buildings, the grounding type of generic cabling system includes 6 parts: grounding wire, grounding bus, grounding trunk line, main grounding bus (main grounding terminal), grounding lead-in wire and grounding body. The corresponding installation positions of these 6 parts can be said to be from high to low (relative to buildings). If they are divided into levels, That is from low to high. However, it should be noted that not all generic cabling systems must have these six grounding types. The following is a brief introduction according to the level of the above grounding wire.

(1) Ground wire

The ground wire is commonly referred to as the ground wire. It is a low-level grounding type connected to the equipment, and it is also the terminal part of the whole grounding system. The grounding wire directly acts on each specific node. The two ends of the grounding wire are respectively connected with the node equipment and the grounding bus to be introduced below, that is, the next higher level of the whole grounding system.

Friends who have experience in copper shaft cable wiring must remember that in copper shaft cable ring wiring, there is an impedance matching terminal at both ends of each line, and the impedance matching terminal usually requires a metal object connected to the ground (usually connected to the metal shell or metal window of the computer), which is grounding, The wire connecting the matching terminal to the computer shell or metal window is the grounding wire. Of course, although the function of the grounding wire introduced here is the same, it is no longer connected to the computer shell or metal window, but a higher-level grounding system. All grounding wires are required to be copper insulated conductors (copper impedance is small, mainly for good grounding), and their cross section shall not be less than 4mm2, and tin welding shall be used as far as possible. Generally, when shielded twisted pair cable is used for wiring, the grounding of information socket can be connected to the distribution cabinet on each floor with the shielding layer of the cable as the grounding wire. When the cables of generic cabling are laid through steel pipe or metal trunking, there is no need for additional grounding. The steel pipe or metal trunking can play the role of grounding, but they are required to maintain good electrical connection and have good grounding at both ends.

(2) Grounding bus

The grounding bus is also called floor grounding terminal. It can also be seen from its name that it is a public grounding terminal specially used in the floor. One end of it shall be directly connected with the grounding trunk line to be introduced later, and the other end shall of course be connected with the grounding wire connected to the distribution frame, distribution cabinet, steel pipe or metal trunking and other facilities on this floor. It belongs to an intermediate level, one level higher than the grounding wire described above, and one level lower than the grounding trunk line described below.

The grounding bus is usually installed side by side with the horizontal wiring system in the floor for the common grounding of the wiring system in the whole floor. The grounding bus shall be copper and its small size shall be 6mm