Structured Cabling  

The History and Organisation of Structured Cabling Standards 

In the beginning there were mainframe computers, made by companies like IBM, Sperry, Univac and Burroughs.  Each computer had cables specifically designed for that computer and its peripherals, e.g. IBM Bus & Tag.

Things didn’t change much until the arrival of Local Area Networks, LANs, which were defined by agreed and open standards in the 1980s.  For the first time datacommunications equipment from different manufacturers could be expected to communicate with each other.  The first LAN to be universally accepted was Ethernet.  This was defined by the Institute of Electrical and Electronic Engineers, the IEEE, within their 802.3 committee.  The first version of Ethernet was 10Base5, designed to offer a 10 Mb/s shared bus using a 50 ohm coaxial cable.  Shortly after came thinnet/cheapernet, which used a smaller coax cable, and was titled 10Base2.

Around 1984, IBM introduced the concept of structured cabling whereby a common set of cables and connectors were installed to wherever people would be presumed to be sitting at some time in the future.  This was also called flood wiring and is the same concept as ordinary telephone extensions.  Before that cables linking mainframes to peripherals were only added as and when necessary.  This made moves and changes very expensive. 

The IBM cabling system was based on a two pair screened 150 ohm cable with a dedicated universal connector.  This product was paralleled by the development of the IBM Token Ring 4 Mb/s LAN which was intended to operate over the IBM cabling System.

Later in the ‘80s, AT&T introduced a cabling system based on standard American telephone components, these being 100 ohm, 4-pair unscreened cable, a cross-connect system based on the 110 Insulation Displacement Connector and 8-wire connector known by its USOC designation as the RJ45.  This is still the basis of most structured cabling systems available today.

Until the beginning of the 1990s, cabling systems were still manufacturer specific, Ethernet was still based on coax.  This changed with the arrival of the 10BaseT standard, whereby Ethernet could now run over 4-pair, 100 cable.  The market really opened up at this stage with many new entrants arriving on the scene.  With no other standards other than 10BaseT however many customers were becoming very confused by competing performance claims from cabling manufacturers.  Anixter introduced a concept of grading cables into levels, as an aid to both purchasing and selling cabling systems.  Level 1 was basic telephone cable and level 3 was the best, 16 MHz grade, for 10BaseT.

Finally, in the early 1990s, standards writing bodies started to pick up on the rapidly expanding world of structured cabling.  ANSI, the American National Standards Institute asked the Telecommunications Industry Association, the TIA, and the Electronic Industries Alliance, the EIA to write national standards.  The TIA changed Levels to Categories and Category 3 was born.  This was closely followed by Category 4 when IBM declared that they needed a 20 MHz bandwidth for their new 16 Mb/s Token Ring LAN.  The cabling standard from the TIA/EIA became TIA/EIA 568.

ISO, the Organisation for International Standards produced ISO 11801 and CENELEC produced EN 50173 for the European Union.  Category 4 had a working life of less than a year after system designers made it clear that 100 Mb/s LANs were on the way, and Category 5 specified to 100 MHz was introduced.  The major standards i.e. TIA/EIA 568A, ISO 11801 and EN 50173 were finally published in 1995, and lasted substantially intact until 1999/2000, when the advent of gigabit Ethernet (IEEE 802.3ab) forced the introduction of enhanced Category 5.  In 2001/2 we saw the publication of Category 6 (a 250 MHz system) and Category 7, a 600 MHz system.

Standards now cover many different aspects of the premises cabling business.  These include:-

Cable System Design

Component Standards

Fire Performance Standards

EMC/EMI Standards

Test Standards

Earthing, Grounding and Bonding

Cable Containment and Administration

Directives and Codes, particularly in Europe, America, Canada and Australia

Local Area Network Standards

All European standards of interest come under CENELEC, which is based in Belgium and set up in 1973 as the officially recognised European standards organisation by the European Commission in Directive 83/189.  CENELEC standards are called European Norms or ENs.  Standards not yet published are called preliminary European Norms or prENs.

Every European country still maintains its own national standards body, such as the British Standards Institute in the UK, but CENELEC standards are adopted as national standards where they exist and then, for example, in the UK, ‘BS’ is placed in front of the ‘EN’ number.  There are some exceptions, such as BS 7718  The Code of Practice for Fibre Optic Cabling, which has no CENELEC equivalent.

In the UK the Fibre Industry Association initiated the BS 7718 Code of Practice.  The IEE, Institute of Electrical Engineers writes the nationally accepted Wiring Regulations (also known as BS 7671), which contains safety issues of power cabling, earthing, bonding etc.

OFTEL was the British ‘Office of Fair Trading for the Telecommunications Industry’.  Their charter stated that they were the:

‘……..independent regulatory body with responsibility for ensuring that holders of telecommunications licences comply with their licence conditions.  OFTEL maintains and promotes effective competition in the telecommunications industry and promotes the interest of consumers and purchasers of telecommunications services and apparatus in respect of prices, quality and variety.’

Oftel’s interest in structured cabling was limited to the maintenance of telephone cabling and the approval of electronic equipment which may be connected to national telecommunications networks.  Such approval must first be sought from BABT, the British Approvals Board for Telecommunications.  OFTEL provided a wiring code and this is addressed in British Standards publication ‘A Guide to Cabling in Private Telecommunications Systems’  DISC PD1002.  There is input to this document from the Telecommunications Industry Association, the British trade association for the telecommunications industry and not to be confused with the American organisation of a similar name. OFTEL was absorbed into OFCOM.

In general, European Union bodies spending large summs of public money should use CENELEC standards, where they exist, to specify their requirements to ensure fair access to that market by all European manufacturers.

CEN is another European body that works in partnership with CENELEC and ETSI.  CEN’s mission is, ‘to promote voluntary technical harmonisation in Europe in conjunction with world-wide bodies and its partners in Europe.’

ETSI is the European Telecommunications Standards Institute in Southern France.  It produces voluntary telecommunications standards in response to requests from its members, currently numbering 700 across fifty countries.

  Copyright Ó annor Ltd   2004