Generic PBX Wiring/Jack question ?

Edwards Finance > Phones

Q. Our PBX is digital and uses a single pair with a standard RJ-11 modular jack. But it's non-standard. I'd like to know, for planning purposes, how many pairs and what is jack type for the standard PBX that are common nowadays? Is it RJ-14 with two pairs, RJ-45 or RJ-48 or whatever with an 8 pin, four pair jack? What are the pairs used for? Power, analog or digital signal(s), and if more than two pair, what's the other used for?

A. If you're running new cabling anyway, make it all Category 5 network-grade cable (4 twisted pairs running to RJ-45 jacks). You can use RJ-45 to RJ-11/14 adapters for your current equipment (or get fancy and make/get custom cables). The reason I suggest this is because (1) it's not much more expensive than running telco-grade 2 or 4 pair wiring and jacks, and (2) the coming generation of PBXes use 10Base-T like digital connections. You can't go wrong by following this advice, I don't think. The cabling I suggest will handle anything you care to do in the next ten years. OK, I guess I'll have to clarify. Seems that everyone wants to be prescriptive, not descriptive. I'll say this, I have to deal with the powers that be. And this isn't a decision that's made by individuals. It's a committee, and that gets really hairy. And to top it off, the Pac Hell will give us a deal we can't refuse, so it's probably gonna be thru them. And they're not known for bleeding edge technology. Also, our 3Com network core is already ATM which may handle voice in the future, so it's possible that the very existing cat5 jacks will be used. In that case, that's already covered by 568, which has nothing to do with what I'm asking! And we've got enough special analog lines, like for FAX and modem, to use a small PBX just for them. But I already know they're a single pair. So back to the situation. I want to know what people are using on the real world, like for a NEAX or Meridian or whatever is the most common PBX, of the 1000 to 10000 line size. I don't wanna know what I _should_ be putting in. We already have cat5 jacks, and I'm asking what I should have for cat3 jacks. Like what should I connect from one end of a (common, as in ubiquitous) PBX to the jack, and what jack. We already have one site that is ISDN and that's all RJ-45. Well, the dummies can't tell the diff between a voice and a data jack. So it's probably gonna be a RJ-11 or RJ-14 jack in the wall, NOT on an adapter. Vertualy all current PBX's use RJ-11 or 14 wiring, and all jacks currently avable are capable of being wired for eather. I always run 4 pair cat 3 home runs from the crossconnects to the station jacks (I never run cat 5 for phones as It's more expensive and provides no advantage) ( with the billions of miles of cat 3 installed you can bank on the manufacturers making their future conventional PBX's backward compatable, Lan switches are another animal all together) this allows atleast 2 spair pairs for furure service, ocasonaly I'll run 6 pair to a location I know will need more pairs. If your switch only uses one pair then the other three are all spairs, for additonal phones , modems etc. The only systems I'm aware of that use RJ-45 's are the older Classic Merlyns and dead dogs like the Horizon and Demention systems. -- dr.d Kiss Technologys The more complicated the plumbing the easer it is to stop up the pipes. I never bother with Cat-3 when inexpensive Cat-5 runs a whopping 1-2 cents more per foot. It just doesn't make sense to stock crap. I terminate both ends with straight pin jacks, 8W8P, even though USOC (6W6P) would work fine. Most phone systems use 1 or 2 pairs, the latter for power and/or signaling purposes. Wiring 4-pair to the station jack gives me the flexibility to use a 2-pair splitter to provide either two TN's or a digital/analog combination from the single jack. Closet crossover cabling from PBX demarcs to back of high density RJ-45 patch panels (via 50 or 100-pair cabling, 2-pair per jack), provides a live TN to the relay rack, which is then patched cabled to the work station patch panel on the same relay rack. Makes for easy MAC work by the customer. My largest customer has a Meridian PBX that uses only 1-pair, regardless of whether the phone has one or two DID's, speaker capability, etc. Beautiful - but expensive - equipment. My smaller customers have Lucent Partner or similar systems - all work equally well with this setup. It assures the customer than any PBX equipment (old or new) will run over their "phone" lines in the future, and that splitting is possible if digital and analog TN's need to be combined over the same wire (regardless if each needs 2-pair). Using 4-pair cabling and jacks makes testing and troubleshooting easier, too, using the same test equipment I use for data. No need to test for polarity (except off the switch). I never wire directly to the PBX's demarc blocks because it results in too much "finger pointing" betwen cabling contractors and PBX contractors. If the PBX people have a live TN off the switch, it's my problem from there if it doesn't stay live to the patch panels and beyond. This system works great where PBX contractors don't want unqualified workers in their phone room. Violates some service contracts.

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