Another change that has come to the fore is how we describe the construction of cables. There are no such cable types as UTP and STP as far as the standards are concerned, they are generic terms. And in the case of the latter, it has caused a lot of confusion. One particular project we have been involved with outlined STP within the Specification Document and when the Installer started to install a U/FTP (no outer foil, with a separate foil around each of the twisted pairs) construction cable, the end client complained that the product was non-compliant. However, this is not correct. U/FTP is a screened cable and STP is a generic term for Screened Twisted Pair, therefore it is compliant. However what the client wanted was an F/FTP (overall foil screen, with a foil screen around each of the twisted pairs) construction but they didn’t make it clear.
We therefore have to be more accurate with our terminology and we have to ensure that clients and their consultants are also clear in their instructions. Excel Networking has produced diagrams of the most common constructions – see the Excel Product Catalogue or Excel Encyclopaedia.
Whilst on the subject of cable constructions, another recent development has been the introduction of a cable that has been supposedly designed specifically for use within Data Centres in cabinet to cabinet links.
The first thing to say is this 26AWG cable complies with Patch and Work Area cord component standards and not that of the horizontal cable, as it cannot support applications up to 90m in the permanent link. This is due to the fact that the attenuation is much greater; in fact all cables meeting the patch and work area cord standards should be de-rated by 50%, thereby reducing any permanent links involved to less than 70m. One manufacturer of such a cable has had their system tested to only provide a channel length of 67m.
Unfortunately, in response, another manufacturer has jumped on the bandwagon. Hopefully there won’t be any others as it is causing an unwelcome level of confusion with those that haven’t been lucky enough to be enlightened to the problems they bring.
They have been put forward on a number of projects as a ‘Horizontal’ cable purely to try and win them on a cost basis without considering the real impact.