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The
Institution of Incorporated Engineers
British
Mensa
http://www.mensa.org.uk/mensa
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address: [email protected]
or
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Current Projects
ISDN
FIBRE OPTICS
STRUCTURED CABLING
INTERNET
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Your Questions and Answers
Richard L. Treat Jr
Hi!
1. What is a structured cabling
system?
2. Who sets the standards?
3. Why is it important?
Thankyou, any information you can assist
me with will be greatly appreciated.
Richard Treat [email protected]
Richard's
Answer
The communications industry
is changing rapidly in an everchanging and demanding business
environment. Offices and building layouts change almost on a daily
basis and the old system of point-to-point cabling meant that the
existing cable infrastucture could not be re-routed easily. In
fact re-routing was time consuming and expensive.
Structured cabling is built
around a network concept where cable can easily and rapidly be
re-configured allowing connectivity between two points.
The structured cable system
allows:
1. Multiple interconnection
points throughout the building
2. A more versatile
re-configuration setup allowing faster, simpler and low cost
connection to any outlet in the network.
3. Support for both data and
voice equipments.
4. Interconnection of
equipment from a wide variety of vendors(Open Systems
Interconnection - OSI).
5. A more uniform and
"structured" cable management.
6. Future as well as present
networking needs.
The original concept of
structured cabling can be based on a University layout or Campus.
One of the buldings in the
campus will hold the Campus distributor, a central patch panel
connected to a server which holds relevant information for all of
the buildings. This central server may be updated from other
Universities via a radio or some other form of communications
link.
The cables fed from the
Campus distibutor then feed the outlying buildings. This cable
infrastructure is known as the Campus backbone cabling (max length
1500m). The cables are terminated within the buildings on a
building distributor. Again this is a patch panel on which may be
connected a server for the building. The building distributor
connects to a series of floor distributors via cables no longer
than 500m. In a proper structured cable design, each floor should
be "flood wired". This means that the floor space on each floor is
divided down into work areas of between 20 - 50 m².
Each work area will be
presented with three to four outlets; usually RJ45. The cables
terminating on any of the distributors can be connected into
either a voice or data device. Cables from these devices will be
presented for use by the user as patch outlets. The voice and data
outlets are normally colour coded such that the user knows that
he/she is plugging in to. Another set of patch outlets will be
connected to the RJ45 outlets via no more than 90m of horizontal
cabling. The user can then pick and choose whether to connect
voice or data or both to each work area.
CABLE
Backbone Cable
There are six cable
standards laid down in ISO specification DIS 11801 as being
suitable for backbone cable:
1. 100 ohm UTP Balanced
(Preferred)
2. 120 ohm STP
Balanced
3. 150 ohm IBM Cabling
system Balanced
or if using fibre...
4. 62.5/125 micrometre
Single mode (Preferred)
5. 50.0/125 micrometre
Multimode
6. 62.5/125 micrometre
Multimode
Horizontal
cable
There are five cable
standards laid down in ISO specification DIS 11801 as being
suitable for horizontal cabling:
1. 100 ohm UTP Balanced
(Preferred)
2. 120 ohm STP
Balanced
3. 150 ohm IBM Cabling
system Balanced
or if using fibre...
4. 50.0/125 micrometre
Multimode
5. 62.5/125 micrometre
Multimode (Preferred)
ISO DIS 11801 specifies that
the maximum horizontal cable length from the Floor Distributor to
the Telecommunications outlet should not exceed 90m. An additional
10m in total is allowed for work area cables, patch cords and
equipmeny cables. Floor distributor patch cables should not exceed
5m in length. Cables should comply with TIA/EIA TSB 36.
Other
Standards
Cable and RJ45 type
connectors must meet the performance standards laid down in
TIA/EIA TSB 40-A, which defines their suitability for transmission
at varying rates as summarised below:
|
Category
|
Freq range
(MHz)
|
Max NEXT at upper
Freq (dB)
|
|
3
|
0-16
|
34
|
|
4
|
0-20
|
44
|
|
5
|
0-100
|
40
|
prEN 50173, EIA/TIA TSB 40,
EIA/TIA 568A and B, EIA/TIA 568A (SP 2840-A) are all other
relevant standards which relate to standard colour coding, cable
lengths and specifications.
More information can be
found at http://www.kroneamericas.com/premis.htm
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Last Revised: 19 Aug 98
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