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

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