owen_mcauley Posted July 2, 2003 Share Posted July 2, 2003 Are there any standard wiring configurations for using cat 5 cable for a comms system? The nice lads in computer services have allowed me to use their existing cable and outlets, however I'm not allowed to change the faceplates for XLR etc. is there a standard, or standard amongst us theatre technicians for wiring comms into cat 5? Cheers Owen Link to comment Share on other sites More sharing options...
James Posted July 2, 2003 Share Posted July 2, 2003 I've seen some verry useful BOB's made up for use with cat 5, 1 box with 4 sets of (1 XLRF 1 XLRM 1 TRS Jack wired in parallel) With a handful of these made up out of odds and ends, you can then use a short patch lead into available cat 5 flood wiring and send your audio wherever you want it. However, This works fine for properly ballanced audio, telephones etc. where the signal is carried on +2 -3. Most Comms systems don't use a ballenced system, they use 1 as ground, 2 as the power supply and 3 for audio. IIRC they also do silly things with signal lights that will do more to screw up everything else. :P So this is great idea for sending audio arround but I think you will have problems if you want to put cans over it. James Link to comment Share on other sites More sharing options...
Rob Posted July 2, 2003 Share Posted July 2, 2003 How would CAT 5 systems cope with the 20 something volts that comms systems usually run on? I presume theyre only designed for low voltage applications. Also, I can't help wondering what happens when someone plugs up a bit of comms gear into the wrong socket and sends 24 volts into the nice expensive hub or switch?? Link to comment Share on other sites More sharing options...
Brian Posted July 3, 2003 Share Posted July 3, 2003 How would CAT 5 systems cope with the 20 something volts that comms systems usually run on? I presume theyre only designed for low voltage applications. CAT5 is fine with 20volts. There is a new standard for powering devices over CAT5 which supplies 48 volts (or is it -48volts?, CBATL). Also, I can't help wondering what happens when someone plugs up a bit of comms gear into the wrong socket and sends 24 volts into the nice expensive hub or switch?? All hubs etc are isolated by transformers so if you pick your pin-out for the comms carefully it'll be ok. Most Comms systems don't use a ballenced system, they use 1 as ground, 2 as the power supply and 3 for audio. This'll cause you the problems, huuummmmmmmm. Remember that comms systems don't even like to share grounds with anything else. Link to comment Share on other sites More sharing options...
owen_mcauley Posted July 3, 2003 Author Share Posted July 3, 2003 It's an internal system which doesn't leave the room, therefore unable to be plugged into a hub/switch, and I've been told that by using all available cores ie doubling up etc the voltage won't be a problem, again I'm only going on what I've been told. Should I just forget this idea then? Link to comment Share on other sites More sharing options...
Brian Posted July 3, 2003 Share Posted July 3, 2003 Should I just forget this idea then? No, there is nothing wrong with the idea. The only likely problem is going to be the lack of screening causing hum on your audio. It's not necessary to double up the cores. It's becoming increasing common to send audio and video over CAT5 as analogue signals, it works fine when they are balanced. Link to comment Share on other sites More sharing options...
James Posted July 3, 2003 Share Posted July 3, 2003 It's becoming increasing common to send audio and video over CAT5 as analogue signals, it works fine when they are balanced. But the problem is that comms isn't balanced. If he were sending anything else then I'd be first to say, yes do it but the thought of sending that unscreened sends shivers, Particularly when there are very cheep alternatives available. Owen, Can you give any more info on the aplication, system used etc. so that we can possible give more appropriate advice? Link to comment Share on other sites More sharing options...
Andrew C Posted July 3, 2003 Share Posted July 3, 2003 I've used unbalanced audio and video on CAT5 without a problem. I concede there is a risk of hum / issues with comms, but perhaps with judicious choice of cores (ref twists) you may get away with it. On the patch panel end you should use a unique coloured patch-lead to avoid ####-ups, and colour code the sockets in use for the comms system. Try an experiment! Then let us all know, it's the way technology moves forwards. Link to comment Share on other sites More sharing options...
owen_mcauley Posted July 3, 2003 Author Share Posted July 3, 2003 Tecpro comms system just being used for beltpacks, single channel only. Master station prompt side and cabled to FOH etc using the cat 5 links. Cable run of around 25m for the furthest point, will only be patched in when required to avoid any mishaps. Owen Link to comment Share on other sites More sharing options...
Brian Posted July 3, 2003 Share Posted July 3, 2003 I think it's going to be a 'try it and see'. As others have said the audio is unbalanced and so it'll be a matter of how mush noise gets picked up by the CAT5 cables. Don't forget to try it with the stage lighting on. Link to comment Share on other sites More sharing options...
Martin Posted July 4, 2003 Share Posted July 4, 2003 We recently discovered that some of our comms were wired with unscreened 4 pair telephone cable. Almost ripped them out with the old telephone system! :P Supprisingly we haven't had any strange hums or buzzes. The runs are 10m-20m. Though we will be replacing them with 2pair screened, as they need re-routing anyway. So this shows that you can run unbalanced down unscreend cable but I wouldn't reccommend it. I would have thought it would be a recipe for disaster, and is probbably just luck that we haven't had any problems thus far. Link to comment Share on other sites More sharing options...
James Posted July 4, 2003 Share Posted July 4, 2003 So this shows that you can run unbalanced down unscreend cable but I wouldn't reccommend it. I would have thought it would be a recipe for disaster, and is probbably just luck that we haven't had any problems thus far. Exactly, I would recomend to anyone planning anything not to use un-screened cable for comms but it will work if you have to use it in an emergency, However it's quality canont be guaranteed nor that it won't wffect anything else in the building. Good Luck Link to comment Share on other sites More sharing options...
delicolor Posted July 4, 2003 Share Posted July 4, 2003 There are no worries with comms voltages on cat 5- it will quite happily handle regular phones (typically 50v DC then up to 90v superimposed AC for ringing) and ISDN/Home Highway lines can be 90-100v DC. Bear in mind Cat 5 is UTP- unshielded twisted pair. There are generally four pairs but the pair to pin grouping is not immediately rational for obscure reasons I can't recall offhand. When we get an IP based comms pack the screening won't be important! The powered standard is interesting- 802.3af, generally provided from ethernet switches (or in-line PSUs in older installations). It is 48v, up to 15.4 watts with short circuit protection & auto discovery (i.e. only applies the power if it senses the end device wants it). Expect to see all sorts of devices accepting this emerging in due course. Ian Link to comment Share on other sites More sharing options...
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