SCS: Standards
SCS standards are provisions documented and establishing at the international level a set of standards applicable to the organization of a structured cable system. The Russian Federation does not have its own requirements for SCS. Organizations involved in wiring cable systems in the Russian Federation are guided by the most convenient and reliable standards in their own subjective opinion - most often these are international standards. There are also European and American standards.
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Prerequisites
The first successful attempt to create a universal cable system was made by the world famous IBM. In the mid-80s, its employees introduced their own version of the CS, which was designed to ensure the viability of various terminals, servers, as well as Token Ring networks. Interestingly, the capabilities of such a system were significantly wider compared to analogues from other companies due to the introduction of elements into the structure that ensured the transmission of telephone signals. IBM's cable system was divided into nine types. Note that this company has never produced cables according to the compiled specifications. This was done by other specialized companies. Among service providers, two types of products were especially popular: a pair of shielded twisted pairs of monolithic conductors in the external screen, as well as a switching cable of two shielded twisted pairs of multicore conductors. However, the cable structure introduced by IBM was not widely used.
This was hindered by several factors, among which the main ones were the high cost and difficulties of integration into modern network systems due to the non-standard wave resistance of the conductors themselves. In addition, IBM tried to focus the specifications directly on its own brand products, which also played a negative role. In addition, at that time, special attention was paid to increasing the data transfer rate directly in local networks. The factors of reliability and cost of equipment, as well as operating costs were taken into account. Market conditions and technological advances contributed greatly to the emergence of a unified system of standards. Twisted pairs were really good material for implementing communication channels in the field of local networks, however, the lack of approved specifications negatively affected the development of the entire direction as a whole.
Current standards
Cable systems of the first generation were developed by companies that were also engaged in the production of computer equipment, components and network equipment. This list included the aforementioned IBM and Xerox. The specialists of these companies, when carrying out work related to design, solved the problems of a fairly narrow circle, in particular, the creation and maintenance of a certain system based on active network equipment from one manufacturer. This approach did not take into account the factor of openness of the configuration, the possibility of modernization, or the versatility of the architecture. As a result, the wiring was extremely highly specialized and differed only in its inherent characteristics and topology. Moreover, the total cost of building such a SCS was quite high, and the need to modernize any part of it meant permanent replacement of the entire cable system. In 1985, the EIA (Electronic Industry Association) began to create its own system of standards for telecommunications cable structures. It is noteworthy that to prepare the necessary documents, several working groups were created from the committee, which was called TR-41.8:
- TR-41.8.1. Cable systems of industrial and office buildings
- TR-41.8.2. Residential Cable Systems
- TR-41.8.3. Communication Cable Channels
- TR-41.8.4. Main CS of residential buildings
- TR-41.8.5. Formalization of definitions and terms
- TR-41.7.2. Building ties and grounding
- TR-41.8.3. Electromagnetic compatibility
The listed divisions developed standards jointly, while each member of the working group who represented any company or organization did not ask for compensation for his work - it was carried out on a voluntary basis. As a result, a package of documents was obtained, reflecting the main aspects of the agreements between the circle of interested parties and companies. In 1988, one of the sectors of the association was transformed into the Telecommunications Industry Association (TIA), which received the status of an independent organization and also took part in the development of a set of specifications. Most standards are still being revised to this day. The study and approval procedure is carried out every five years. The first set of standards was published in the fall of 1990. The document was called the TIA/EIA-569 "Standard for commercial buildings for cable routes of telecommunications cables." It was developed by the TR-41.8.3 group. Due to the impossibility of competent construction of the SCS, which will function with high efficiency, without studying the features of the building and presenting special requirements, the adoption of such a resolution was extremely necessary.
Another type of twisted pair classification was proposed in 1989 by the well-known American association Underwriters Laboratories (UL) in conjunction with Anixter. The division was based on the concept of level. In total, five levels were proposed, which differed primarily in the maximum signal frequency. In turn, the TR-41.8.1 working group proposed the "Standard for Telecommunications Cable Systems of Commercial Buildings" TIA/EIA-568. It was approved in July 1991. The document itself determined the structure of the SCS, the requirements for the connectors and characteristics of the cables themselves, and also established restrictions on their length and section. In 1995, ISO and IEC associations approved ISO/IEC 11801 Information Technology. Cable system for buildings. " This document is an alternative cable standardization package in Europe. In principle, both documents have minor differences in content.
The difference concerns, first of all, the terminology and structure of the document. In turn, the European Committee approved its own provisions specified in document EN50173 (EN - Europa Norm), the final version of which was published in August 1995. An English copy of this list is actually a copy of the international version. All three standards are generally close to each other and detail the construction features and elementary content of the SCS bases regarding the cable structure. The differences between them are unprincipled, and some of them, the most significant, we indicated in the table. In practice, either American or international standards are most often used. They are most common and, thanks to the active cooperation of members of organizations on both sides, have the least differences.
Cable requirements
According to the international standard ISO/IEC 11801, only symmetrical electrical cables based on twisted pair with wave impedance of 100, 120 and 150 ohms in shielded and unshielded form, as well as single-mode and multimode optical cables are allowed in the SCS. Optical cables are rarely used in the horizontal subsystem, although the share of such constructions in the total volume increases very quickly. In the internal trunk subsystem, both types are used quite often. Multimode fiber-optic cables serve mainly as the basis of the internal backbone subsystem. Single-mode fiber optic cables are recommended only for long external trunks. In turn, we note that coaxial cables are not included in the number of ones allowed for use in the new standards and are gradually excluded from the next editions of the old ones. This is explained by the fact of distrust of the low reliability of networks built on the basis of coaxial cables, as well as a low level of manufacturability and a higher cost compared to cables based on twisted pairs.
International Standardization Organizations
In addition to numerous associations founded by representatives of American firms and companies, there are several global structures that have outlined their conditions and standards for the SCS. We are talking about the international ISO standardization organization, as well as the international electrotechnical commission, better known as IEC. They also participate in the development of a set of standards in other technical committees. Both of these associations form a body that is recognized around the world - other structures willingly interact with them in related areas. The International Electrotechnical Commission, as well as the international standardization organization, established the ISO/IEC OEC 1 Technical Joint Committee, which specializes in the field of information technology. Projects approved by him are transferred to other national organizations, which by voting determine the further fate of the document or standard.
It should be noted that at least 75 percent of the approval vote is required to adopt a standard. There is also a European committee for the standardization of electrical engineering called CENELEC. This organization operates regionally and works closely with the International ISO Standardization Organization. Countries that provide support to the CENELEC committee recognize the standards approved by the working group of this structure, without any changes. European standards are presented as documents in three languages: English, French and German. Translations into languages of other countries are also possible. Certified by the Central Secretariat, they receive the status of official versions. The main international and European standards are practically the same, however ISO, IEC, as well as CELENEC in related areas develop their own standards. Thus, in European states, their own parameters of shielded and fiber-optic cables have been determined.
Russian SKS standards
Our country does not have its own SCS standards and cable nomenclature. As a regulatory framework, domestic specialists rely in most cases on world standards. There are several reasons for this. To begin with, we note that the Russian Federation is a member of ISO and IEC organizations. The European standard seems to be the least convenient for Russian installers, since the Russian Federation is not a member of the European Committee for Standardization in the field of electrical engineering. Targeting American standards is also not very convenient, as TIE/IEA is one of many national standardization sets. Moreover, the use of an international standard is beneficial to domestic companies in terms of business. In this case, the company providing services can guarantee its customers legal protection no longer at the regional, but at the world level, albeit representing one of the most capacious parts of the SCS market.
Links
Full list of European, international and American standards
Course "Introduction to CMS based on copper twisted pair and fiber optics"
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