Myth No.16 ~ 'Transmission distances are limited'

A range of transmission options can now be used that allow any distance limitations to be overcome. 

Category 5 cable (known as Cat 5) is a twisted-pair cable type designed for high signal integrity. On many sites it has now been superceded by the Category 5e specification, an enhanced version (though it is often still called Cat 5). Cat 5e is often used in structured cabling for computer networks such as Ethernet. Cat 5e cable does not enable longer cable
distances than Cat 5 for Ethernet networks, and cables are still limited to a maximum length of 100 m (328 ft). Category 6 cable (Cat 6) is designed for Gigabit Ethernet and is backward-compatible with category 5/5e. Cat 6 features more stringent specifications for cross-talk and system noise. It is suitable for 10BASET / 100BASE-TX and 1000BASE-T (Gigabit Ethernet). It is expected to suit the 10GBASE-T (10Gigabit Ethernet), although with limitations on length if unshielded Cat 6 cable is used. The maximum length of a Cat-6 horizontal cable should be 100 m (330 ft).

It is possible to run Ethernet data over coaxial cable using cost-effective adapters to convert the signal for coaxial cable transmission. This method is often
used on legacy sites where existing coaxial cables for CCTV have already been installed. By combining Cat 5 twisted-pair cable and RG59 coaxial cable, transmission distances of up to 350 m can be achieved.

Using fibre optic cable is the best way to extend transmission distances, particularly when legacy cable is not available. Choose ruggedised, professional transmitters and receivers to convert the signals for fibre transmission, and look for well-made products that combine network switching with media conversion.

Multi-mode fibre is a type of optical fibre mostly used for communication over shorter distances, such as within a building or on a campus. Multi-mode fibers support applications from 10 Mbit/s to10 Gbit/s over link lengths of up to 4 km - more than sufficient for most premises applications.


The trend, however, for Ethernet applications is to use the more precise single-mode optical fibre solution. Transmission distances of up to 40 km are achievable for a relatively small increase in equipment costs. 

This has the additional advantage of being electrically inert, and is immune to electromagnetic interference. The traditional coaxial cables used in analogue CCTV systems could be plagued with interference problems, particularly on large sites with earth loops, different electrical phases, and often heavy electrical plant, all combining to cause signal interference and image deterioration. Optical fibre is not affected by any of these problems.