Ike Posted March 8, 2008 Share Posted March 8, 2008 When wiring a venue with UTP and 8P8C 'RJ45' sockets what's the consensus on the number of pairs that should be wired to each socket? I'm looking at a venue at the moment that wants quite a lot of cabling installing initially for DMX and Ethernet (10/100 Base). The building in question is listed and has a lot of tight cable runs so it would make my life a lot easier if I could use one cable per double socket however I'm a bit concerned about future proofing and the potential for loosing half the sockets if the need for four pairs arose. In terms of lighting, RDM etc. does anyone think it likely there will be a need for four pairs any time soon, say over the next four or five years? Link to comment Share on other sites More sharing options...
bruce Posted March 8, 2008 Share Posted March 8, 2008 It would not meet the CAT5 standard. I'd be very wary of doing anything other than terminating all 4 pairs, if only because the standards say you should terminate all 4. Yes, only 2 pairs are needed for Ethernet,, phones, DMX etc and I'm sure you could put together a reasonable argument for doubling up, but imagine the situation a couple of years down the line when the people who are aware of this argument have moved on, and someone "discovers" the "problem". They'll think "look what that cowboy has installed". I manage an installation with (at the last count) somewhere in the region of 16,000 connections. Every one was installed to the standard. Yes, that means that half of the wires are unused. It also means that the cable tester doesn't flash up "wiremap fault" every time it's plugged in :-) Bruce. ps - there are some devices on the market that DO use all 8 cores - video/audio-over-UTP units are the ones that come to mind, as well as some (now thankfully obsolete) proprietory HP ethernet kit. Power-over-ethernet devices may or may not use all 8, depending on which flavour they are (midspan or endspan) Link to comment Share on other sites More sharing options...
landy Posted March 8, 2008 Share Posted March 8, 2008 To add to Bruse's thoughts, some lighting (as we are in this forum) is using all 4 pairs. For example some LED par 16 are. Link to comment Share on other sites More sharing options...
Tomo Posted March 8, 2008 Share Posted March 8, 2008 Gigabit Ethernet uses all the pairs, and as Bruce mentioned there are several devices on the market that also use them all.The DMX-over-Cat5 standard actually calls for three pairs - admittedly the second data link is rarely used, but there is probably some kit that does. Wire it to the standard (EIA/TIA 568B), as it will cause problems later on if it's not. It is much, much cheaper to pull cable at the initial stages of the project than to add cables later on - this is particularly true if space is tight, as it's easier to tie the bundle together and pull it through as one unit than to try to squeeze an extra cable down an already-populated conduit. Link to comment Share on other sites More sharing options...
Soundie Posted March 8, 2008 Share Posted March 8, 2008 Gigabit ethernet requires use of all four pairs, with more and more kit being supplied as standard as gigabit, and the fairly low price of gigabit switches etc. I would be very wary of putting in anything other than all four pairs. It really restricts what might be needed in the future. I would also suggest that you always put in more network points than you think you need at the moment, as there is always that time where you wish you had more. My rule of thumb is to think of how many sockets would be required within the next year, and then double it. ------ Beaten to it by Tomo Link to comment Share on other sites More sharing options...
bruce Posted March 8, 2008 Share Posted March 8, 2008 How on earth did I manage to forget to mention gigabit. Doh! Having said that, the technology is usually smart enough to realise that if you try to use Gb and you only have 2 pairs available, then it will fall back to 100Mb/s. So plug a 2pair into you nice shiny Gb switch, and it should work, but at lower speed. Many people will not realise that it's going slower... Link to comment Share on other sites More sharing options...
Ike Posted March 9, 2008 Author Share Posted March 9, 2008 Thanks for the comments so far. While I knew gigabit required four pairs I'm not really sure I see how it might be required in your average venue apart from maybe as a backbone to link switches and servers, does anyone really need that much bandwidth? I'm not sure PoE is that relevant as there will be mains available wherever UTP is. Video and audio requiring four pairs would be a bugger, I take it this is fairly common? :) To be honest I was kind of hoping it would be like the second pair for DMX where it's so rarely implemented everyone's forgotten about it. Damn. Tomorrow I will be mostly trying to shove a round peg in a square hole... Link to comment Share on other sites More sharing options...
Sam Jelfs Posted March 10, 2008 Share Posted March 10, 2008 I think what people are generally saying is that yes, you only need two pairs, but why install a system that is only capable of running (most of the) current technology, and not allow for improvements when new technology that uses all 4 pairs is available. When it comes to bandwidth, with higher resolution video systems becoming more commonplace the bandwidth needed for them is only ever going to increase. Link to comment Share on other sites More sharing options...
Ike Posted March 10, 2008 Author Share Posted March 10, 2008 I think what people are generally saying is that yes, you only need two pairs, but why install a system that is only capable of running (most of the) current technology, and not allow for improvements when new technology that uses all 4 pairs is available. Because The building in question is listed and has a lot of tight cable runs so it would make my life a lot easier if I could use one cable per double socket... ;) As it goes I managed to get four pairs to everything apart from the sockets on a couple of bars. These are clearly labeled and documented and all it would take to convert to four pairs would be swapping the double sockets for singles and a minor adjustment at the other end. Needless to say the client is fully aware (and fully supports) my decision. Link to comment Share on other sites More sharing options...
bruce Posted March 10, 2008 Share Posted March 10, 2008 These are clearly labeled and documented and all it would take to convert to four pairs would be swapping the double sockets for singles and a minor adjustment at the other end. Needless to say the client is fully aware (and fully supports) my decision. A slightly more standards-compliant (although less neat) way of accomplishing the same thing would have been to use a single socket with all pairs wired, and a couple of cat5 "cable economnisers" - eg CPC part number cs13200http://cpc.farnell.com/productimages/farnell/standard/CS1320006-40.jpg Link to comment Share on other sites More sharing options...
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