SCS: Standards
The SCS standards are the provisions recorded dokumentarno and setting a complex of the standards applicable to the organization of a structured cabling system at the international level. In the Russian Federation there are no own requirements to SCS. The organizations which are engaged in distributing of cable systems in the Russian Federation are guided by the most convenient and reliable standards in their own subjective opinion - most often it is international standards. There are also European and American standards.
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Prerequisites
The first successful attempt of creation of a universal cable system was made by world famous company IBM. In the mid-eighties her employees submitted own version of KS which was intended for ensuring viability of different terminals, servers and also networks of the Token Ring format. It is interesting that possibilities of such system were significantly wider in comparison with analogs from other companies due to implementation in structure of elements which provided transfer of telephone signals. The cable system of IBM was separated into nine types. Let's note that this company never made cables on the made specifications. Other profile companies were engaged in it. Among service providers two types of products enjoyed special popularity: pair of shielded twisted pairs from monolithic conductors in the external screen and also a switching cable from two shielded twisted pairs from multicore conductors. However the cable structure provided to IBM was not widely adopted.
It was interfered by several factors among which the main were the high cost and difficulties of integration in modern network systems because of the non-standard wave resistance of conductors. In addition in IBM tried to orient specifications directly on products of own brand that also played the negative role. In addition we will note that at that time special attention was paid to data transmission fall forward directly in the local area networks. Factors of reliability and cost of the equipment and also operating costs were considered. Market conditions and technology progress in many respects promoted emergence of a single system of standards. Twisted pair cables were really good stuff for implementation of communication channels in the field of local networks however the lack of the approved specifications had negative effect on development of all direction in general.
Current standards
Cable systems of first generation were developed by the companies which were also engaged in production of the computer equipment, component parts and network equipment. This list included above-mentioned IBM and Xerox. Specialists of these firms at work connected with design solved problems of rather narrow circle, in particular creation and ensuring functioning of a certain system based on active network equipment from one producer. At such approach neither the factor of openness of a configuration, nor a possibility of upgrade, nor universality of architecture were considered. As a result wiring turned out extremely highly specialized and differed only in it in inherent characteristics and topology. Besides, the total amount of costs for creation such SCS was rather high, and need of upgrade of its any part meant permanent replacement of all system of cables. In 1985 EIA (Association of the electronic industry) was engaged in creation of own system of standards for telecommunication cable structures. It is remarkable that for preparation of necessary documents several working groups of committee which received name TR-41.8 were created:
- TR-41.8.1. Cable systems of industrial and office buildings
- TR-41.8.2. Cable systems of residential buildings
- TR-41.8.3. Channels of communication cables
- TR-41.8.4. Trunk KS of residential buildings
- TR-41.8.5. Formalization of determinations and terms
- TR-41.7.2. Construction sheaves and grounding
- TR-41.8.3. Electromagnetic compatibility
The listed divisions developed standards jointly, at the same time each workgroup member who represented any company or the organization, did not ask for the work of compensation – it was carried out on a voluntary basis. The document package reflecting the main aspects of arrangements between a circle of interested persons and the companies was as a result received. In 1988 one of sectors of association was transformed to Association of the telecommunication industry (TIA) which received the status of independent organization and took part in development of set of specifications too. The majority of standards are reviewed to this day. The procedure of studying and a statement is held each five years. The first set of standards was published in the fall of 1990. The document received the name TIA/EIA-569 "The Standard for Commercial Buildings on the Cable Ways of Telecommunication Cables". It was developed by TR-41.8.3 group. Due to the impossibility of competent creation of SCS which will function with high efficiency without studying of features of the building and presentation of special requirements, adoption of such resolution was extremely necessary.
One more type of classification of twisted pair cables was offered in 1989 by the known American association Underwriters Laboratories (UL) together with Anixter company. The concept of level was the basis for separation. In total five levels which differed first of all with the maximum signal frequency were offered. In turn, working group TR-41.8.1 offered "The standard of telecommunication cable systems of commercial buildings" TIA/EIA-568. It was approved in July, 1991. The document defined structure of SCS, requirements to connectors and characteristics of cables and also set restrictions for their length and section. In 1995 ISO and IEC associations approved the ISO/IEC 11801 standard "Information technologies. A cable system for buildings". This document is an alternative packet of standardization of cables in the territory of Europe. In principle, according to contents both documents have insignificant differences.
The difference concerns, first of all, terminology and structure of the document. In turn, the European committee approved own provisions specified in document EN50173 (EN — Europa Norm) which final version was issued in August, 1995. The English-language copy of this list actually is the copy of the international version. All three standards are in general close to each other and in detail specify features of creation and the elementary maintenance of bases of the SCS concerning cable structure. Differences between them are not basic, and some of them, the most essential, we specified in the table. In practice either the American, or international standards are most often used. They are most distributed and, thanks to active cooperation of members of the organizations on both sides, have least of all differences.
Requirements to cables
According to the international standard ISO/IEC 11801, in SCS use only of symmetric electric cables on the basis of the twisted pair cable with a wave resistance of 100, 120 and 150 Ohms in a screened and unshielded type and also single-mode and multimode optical cables is allowed. Optical cables are rather seldom used in a horizontal subsystem though the share of such constructions in total amount increases very quickly. In a subsystem of internal trunks both types are used rather often. Multimode optical fiber cables serve, generally as a basis of a subsystem of internal trunks. Single-mode optical fiber cables are recommended to be used only to creation of extended external trunks. In turn we will note that coaxial cables are not switched on in number permitted to use in new standards and are expelled gradually from the next editorial offices old. This fact of mistrust in comparison with cables on the basis of twisted pair cables is explained by low reliability of the networks built on the basis of coaxial cables and also low level of technological effectiveness and higher cost.
International organizations of standardization
In addition to the numerous associations founded by representatives of the American firms and companies there are several world structures which designated the conditions and standards for SCS. It is about the international organization of standardization of ISO and also the international electrotechnical commission better known as IEC. They also take part in development of a packet of standards as a part of other technical committees. Both of these associations form body which is recognized around the world – other structures willingly interact with them in adjacent areas. The international electrotechnical commission and also the international organization of standardization founded the Technical joint committee ISO/IEC OEC 1 which specializes in information technology field. The projects approved by it are transferred to the other national organizations which by vote define the future of the document or standard.
It should be noted that adoption of this or that standard requires not less than 75 percent of votes of approval. There is also the European committee of standardization of electrical equipment under the name CENELEC. This organization works regionally and closely cooperates with the International organization of standardization of ISO. The countries which give support to CENELEC committee, recognize the standards approved as the working group of this structure without any changes. The European standards are presented in a document type in three languages: English, French and German. The translations and into languages of other countries are possible. Certified of the Central secretariat, they receive the status of official versions. The fundamental international and European standards practically match, however ISO, IEC and also SELENEC in adjacent areas develop also own standards. So, in the European states own parameters of shielded and fiber optic cables are determined.
Russian SCS standards
In our country there are no SKS own standards and the cable nomenclature. As the regulatory base domestic specialists rely in most cases on the international standards. Reasons for that a little. For a start we will note that the Russian Federation is a member of the ISO and IEC organizations. The European standard seems to the least convenient for the Russian installers as the Russian Federation is not a member of the European committee on standardization in the field of electrical equipment. Orientation to the American standards is not too convenient too as TIE/IEA – one of many national sets of standardization. Besides, use of the international standard to profitable domestic companies in terms of business. In this case the company providing services can guarantee to the customers legal protection not on regional any more, and at world level, let and representing one of the most capacious parts of the market of SCS.
Links
Complete list of the European, international and American standards
"Introduction to SCS on the basis of the Copper Twisted Pair Cable and Fiber Optics" rate
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