Specifications

G
G1
STRUCTURED
CABLING
NETWORK CONNECTIVITY SYSTEMS
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History
Until the beginning of the 1980’s, the majority of computer networks worked in the host/terminal mode.
Applications as well as data were stored centrally on a host computer and user stations, so-called terminals,
handled them in this centralized way. Considering the text character of this type of communication, it was not
necessary to build special high capacity transmission paths in terminal networks.
The prevalence of terminal networks ended in 1981 when IBM launched their first personal computer onto
the market. This new type of work station, which, contrary to terminals, was equipped with a local memory
and their own outputs for connecting peripherals, meant a different—decentralized—mode of operation for
users. This greater independence, however, brought two important issues,
1. Difficult administration of workstations (i.e. problem solving and software installation).
2. Mutual user cooperation.
It was therefore necessary to find a way that would enable to connect the new PC’s into a network, through
which it would be possible to share files, applications, and costly peripherals in the same manner as it had
been previously on terminal networks.
In the beginning, several solutions arose from different producers. The differences in applied technologies
and the diversity in the components of these new systems, however, led to their mutual incompatibility.
The solution was to design a universal system, which would set recommended standards determining the
electrical and physical characteristics of cables as well as connecting hardware. At the beginning of the
1990’s, therefore, the American National Standards Institute (ANSI) asked Telecommunications Industry
Association (TIA) and Electronic Industries Alliance (EIA) to propose a uniform standard for cabling systems.
One of the most suitable ways for the new cabling system design was to use the already existing solution
introduced by the American telecommunication company AT&T. These networks used AT&T’s telephone
distribution systems that were installed in most administrative buildings. They had a star topology and used
a twisted pair cable as the main transmission medium. The outcome of the Standards Commission work was
the first specification for structured cabling, which was published in July 1991 and was referred to as
ANSI/TIA/EIA 568. Together with technical bulletins TSB-36 and TSB-40 issued a little later, the standard
defined the basic transmission requirements for Category 3, 4, and 5.
In 1995, the first update of the above mentioned standard and also the first version of an international
ISO/IEC 11801 standard were issued. A year later, in 1996, the organization CENELEC published the first
European standard for structured cabling, with the designation EN 50173. As a result of a new high-speed
protocols development (e.g. Gigabit Ethernet), these standards were updated in 2000 and 2002. The updates
defined new parameters, which must be met by structured cabling components in order to comply with the
new protocol requirements. The standards were supplemented with further measured or numerated
parameters, such as PSNEXT, PSACR, PSELFEXT, Delay Skew, and so on. In these specification updates
new Category 5 (today known as Category 5E, please see bellow for more information), and later Category 6
as well as Category 7, were introduced.
Introduction to Structured Cabling