atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services T1's, CSU's and DSU's Installing T1 from Demarc

I have been around the "normal" network cabling world and POTS stuff, but this is my first T1 job. I am going to bring up T1 service from the Demarc to a Cisco router. I am worried that the LEC hasn't put in RF45 jacks at the Demarc for me to plug into(then run a cable to the router) All that being said, if I have to install my own jack which lines will go under which screw terminal at the demarc? I know there are four wires, but what pairs are going to what terminal. Hope I havent confused anyone too much.

Thanks in advance,

Travis

The telco demarc is typically a smartjack. You just plug a patch cable in from there to your router.

Thats what I am hoping for...But if not? I would have to wire up some sort of a jack I think

The "smart jack" may be located on a small cabinet that houses cards in it. Most of the cabinets used by SBC and Verizon in my area will have 2 RJ45 ports underneath the cards on them. If there is only one card you will plug into the first RJ45 port usually labelled "1" or "a".From there you will plug a patch cable TO the WIC card on the cisco router.If you are too far to run a patch cable you will need to install a cat5 line from point to point. I usually then wire both RJ45 jacks as 568b and connect patch cables at either end.

You will get a green CD light on the WIC card that is in the router if everything is working correctly.

There is usually a small card in a pocket on these cabinets that will have your circuit ID on it.Verify your circuit I.D. as a matter of habit. I have seen guys banhg their heads againt the wall to find out they have been messing with the wrong circuit.

It's possible...T1 comes in normally on an RJ48C or RJ48X. RJ48X has shorting bars for when the cable is removed.
This uses pins 1, 2, 4, and 5.
1 and 2 are a pair, 4 and 5 are a pair.
Hope this helps!

In Rockford and surrounding area this is about the only way you'll see them now. The majority of T1s I deal with now are for subcontract work for national companies. The last three dozen (or more)T1s I have worked with have been installed in this matter.

The same thing at the last 12 Edward Jones locations I installed Cisco routers for.

I can't even remember the last time I connected directly to a "smart jack" for a T1.

Around here I only see smartjacks.

Wierd, I wonder why the switch in this area?
I was never in the DOG(changed names a few times) when I was at IBT/AMT/SBC/ATT so I can't say why they went from using the "smart jacks" to these. I should call one of my old co-workers and ask I guess.

I don't know a tremendous amount about the technical aspects of the T1 itself.Pretty much basics is all I needed to do my work with them. I did prep lines for circuit use and I have repaired the outside plant copper lines that carry them in.I've worked with guys on repeaters etc.Never really cared too much to be honest I have not actually installed one by myself. I do connect to them quite often in the course of the work I do now though.

I believe the ports in the cabinets are Rj48c. I'll take a picture of one and post it here so people know what I'm talking about.

An RJ48X is a smart jack. I think we are confusing this with a network termination unit or network interface unit. This is a card in a shelf or single mounting that belongs to the telco. Yes, the output of this card is considered a "smart" jack, but it can be extended beyond this point to another "smart" jack. The key is maintaining loopback.

The term "smart jack" just implies that it automatically creates a loopback condition between transmit and receive when the equipment is unplugged. That's all; nothing else. There are no cards that constitute a smart jack. For all intensive purposes, some circuits come into RJ48S jacks directly from incoming cable pairs. There's no magic going on. The card/shelf is only there to condition cable pairs from long loop lengths.

Ed, when I meant smartjack, I mean the cabinet on the wall with the special key and the circuit card. That's what I was always told they were called

That is what they are referred to as Smartjacks.

They are basically a loop point the telco can loop to. They convert depending on the model the signal that is coming in to TDM so that our equipment can use it. There are also differnet models that are dum smartjacks that just regen the signal and create a loop point. Those are not very common anymore around here. None of the actual Smartjacks that you are refering to will go into loop back when the customer unplugs. Only when a FAC2 loop signal is sent down the line. The RJ48X will. Some telco's have started deploying these to prevent carrier alarms in there switch when the customer unplugs. Plus is gives them another test point outside the NIU. that test thru all the circuitry and the NIU case.

It's possible that it's different depending on the part of the country.

Fellers, to be technically correct a SmartJack is a NCTE (Network Channel Terminating Equipment) that was produced for the analog data days… It was a self aligning, auto balancing unit made by Westell (I think… I could be wrong on the manufacture here been a long time since I’ve even thought of one of those)

The generic term smart-jack has come to be applied to all NCTE or NID (network interface device) equipment for special service circuits. The generic term smart-jack can be used for the card terminating at a customer premise for analog data or voice trunks, DS0 DDS (9.6 to 64 Kb digital data service,) Fractional T1, up to Hi-Cap DS1 (T1.) Most any of these devices perform the same basic tasks of auto-aligning, loop-back on command for testing, remote testing, sink of DC current.

The outputs of these units are modular jacks that are pinned to RJ-48S (for DS0) and RJ-48C (for DS1)… The RJ-48X is pinned the same as a 48C except that the “X” will automatically loop-back. This is not the so called smart function, a modular jack can do this and it’s not a smart-jack in the generic nor the literal use.


To smart-jack or not to smart-jack on a digital circuit…. That is the question.

Ask me, I say put smart-jacks on EVERYTHING. Regardless of the DDS speed/size service it can allow for some remote testing with no “truck roll” required… As I mentioned above it they can do, auto-aligning, loop-back on command for testing, remote testing, sink of DC current all aide in the tern-up and maintenance of circuits… and last but not least, in today’s delivery of Digital services over copper loop these units are REQUIRED to reformat the digital signal coming off the copper spans. Digital signals are often reformatted at the C.O. to allow for longer reach (HDSL) or full-duplex over one pair (HDSL2 or Total-Reach) and then have to be converted BACK to its original usable format at the smart-jack.

The term “Smartjack” is just more abused jargon. To really know what is meant by the term, you just need to keep it in context of the person speaking, their back ground, age, profession, resume, experience and the conversations origin. Then ask "What the hell are you talking about!"

This usually clears up any miscommunication.

Just like "RJ45", buzz words are just buzz words, however inaccurate they may be with regard to the situation.

Thank you Bryan and SST for joining my crusade.

Note to self: Shut up Ed!

Useful info. Thanks guys!

Hello, new guy here. I am a comm tech with the bigger phone company who's name I would rather not disclose. But to give a hint...we now use lower caps in our initials. RJ48C and RJ48X jacks are what we commonly test to when lecs deliver T1 access circuits. The 48X is what we refer to as a smart jack because of the loop back condition it presents to the network; when nothing is plugged into the equipment side.

One disadvantage I have when testing to a smart jack (when the installer is not onsite) is not being able to prove that I am actually running to that 48X loop. The lec's C.O. could have their DSX or DACS looped or my C.O. could also have a loop up. I make it part of my process to call the lec and have them break the circuit just before the 48X so I can see it go open. Some lecs are irritated when we doubt their assurance that there's no foreign loop in the circuit but I would rather irritate them than the customer at cut-time. The loop-able 48C is obviously my NIU of choice.

I just realized my contribution may not be relevant but it seems a waste not to post it.

It may take awhile but we'll figure out the big company you work for. From your post I also assume you work in provisioning. Stop by the Phone Booth and introduce youself in the new members post.

Hi guys,

I extended a T1 this week that I have having some problems with. It's an outdoor unit with the 4 terminal screws with the pig-tail. I know it's pins 1-2 & 4-5. Green and red should be pins 4-5 right? Black and yellow are 1-2? I have this going to a 568B jack. The problem is that they can't see the router from the HQ. I have a carrier display light on the router, so would that tell me my wiring is correct? Or do I have some pins crossed? Any help would be great, it's been on my mind the whole weekend.

Try it the other way around and see if it works
I'm pretty sure it's red/green on 1 and 2, black/yellow on 4/5.
Jeff

OK, I'm sure I'll find out tomorrow if it's still down. Then I'll try it the other way. Thanks.

Another thing to do is take a fluke. Make sure you show a short across Pins 1&2 and across 4&5. If you only have 1 conductor passing thru on 1 of the pairs a lot of equipment will show carrier but will not come up. This should prove your cable and heads are good but your pairs may be reversed. Normally on a outdoor mount around here atleast if you are needing a straight thru cable then Red/Green would be Blue/White and Yellow/Black would be Orange/White. This should give you a straight thru cable.

If this was handed off to you correctly the first pair should be the receive from Telco and should go on pins 1&2. First pair in the case you are discribing is red/green

T1 is up. Thanks guys.

Kevin,
That's great news! Can you share the "fix" with us? Was it simply a matter that the transmit and receive pairs (1&2 / 4&5) were reversed?

Actually a couple of things. I did have the pairs backwords on the terminals. After switching them around it still wouldn't come up. After putting a hard loop at the NIU, the tech could see the loopback. So I knew that was fine. Did the same thing at my jack going to the router, also good there. Turned out to be a bad patch cord from my jack to the router. Brand new cord too. Swapped it out and it came right up. They also had ISDN back-up which may have helped trouble-shooting.

Thanks for the update, Kevin. :thumb:

I will be extending a T1 from Demarc to Office. I beleive they will bring the T1 in the basement and I will have to run telephone lines and the T1. I plan on running cat5e (4pair) ... 3 lines for telephone and 1 line for T1. I never installed a T1 before so this will be new for me. My guess is that I will wire a cable with an 8 pin modular plug on each end also known as "rj45" with t568b on both ends and that will plug directly into router from smart jack?

Will I have to have any special jacks or plugs?

RJ48X (smart jack) is what the telephone company will install correct?

So basically i will be creating a very long patch cable. Will this work?

Yes it will work.

Thats pretty much it Irvin.

thanks for your help. I will let you know the outcome.