atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services T1's, CSU's and DSU's T1 circuit question for T1 experts

Customer has a T1 circuit in a nice, multi tenant office building. In the basement Verizon has their main terminal. There is a 300 pair copper cable from the street. All sorts of fiber optic equipment (fiber patch panels, power supplies, ADC Remote Terminal's plus some Canoga perkins fiber units. This customer has a T1 circuit bought through a reseller of a reseller, some company I never heard of and has nothing but trouble, outages etc. Their phone company says it's a copper T1 and subject to failure because of old failing cable. I told the customer, doesn't matter, it's phone company's responsibility to fix it.

Their circuit comes out of a cabinet with a glass front filled with T1 circuit cards and there 12 positions to plug in with a patch cord on the side of the cabinet going to their suite. There are also two 25 pair cables feeding into that cabinet. I believe those 25 pair come from the ADC remote terminal. I believe that ADC remote terminal is fed by fiber from Verizon.

I say to the customer I am pretty sure that is all delivered to you by fiber optic cable, not copper. I do not consider myself a T1 / telco expert so I am looking for some input or opinion.

Back when I worked as a CO tech for an IXC/CLEC, LECs would install pair gain units on copper T1s. Does such a device exist at the customer prem? Did the LEC install a 48X or a 48C jack?

No smart jack, long piece of Cat5e from their suite to this T1 cabinet (we'll call it a T1 cabinet) in the basement.

I looked up the ADC Remote terminal and it is some sort of fiber to copper device. I see them everywhere, in every office building.

The rack you described filled with T1 cards is the smart jack. I see them once in a while but I mostly see the 4 card rack.

My understanding is the everything after the output of the Smart Jack is the customers responsibility.

These racks and mountings often include RJ48X/S jacks that have been named "smart jacks" because they are equipped with shorting bars that bridge the transmit and receive pairs together when the plug is not inserted in order to keep the circuit alive. There are a few things that need to be considered when extending a circuit from them.

First, the maximum cable length on the CPE side of the network termination card (basically at the "smart jack") is 655 feet. That's 655 perfect feet, as in a cable that is run in a straight line, has no kinks, twists or sharp turns.

Next, this 655 foot maximum length is determined by padding on the network termination card itself. These settings vary from 0 feet to 655, and it must be set by the telco technician when the circuit is installed. Since the telco's responsibility ends at the RJ48 jack, they often don't change the default setting, which is for circuits under 100 feet (don't quote me on that).

Lastly, it is standard practice for the extended circuit's transmit and receive pairs to run under separate cable sheaths. In multi-pair riser cables, they would accomplish this by placing the transmit and receive pairs in separate binders within the cable. ANY form of separation is better than none. In your case, there should be two cables extending this circuit. In the case of multiple circuits, all of the transmit pairs can be in one cable and all of the receive pairs in the other. Shielded cables are even better, assuming that the shields are properly grounded and bonded so that external interference is minimized.

With a single CAT5 cable used as the circuit extension, combining transmit and receive within the same jacket can lead to the circuit actually interfering with itself. This can lead to all kinds of phantom issues that are impossible to trace.

Remember that CAT5 or greater cable is a lot longer copper-wise due to the tight twists in the pairs. 300 feet of CAT5 cable can easily be the equivalent of 500 feet of CAT3. People think that CAT5 cable is "better", but actually in these instances, the added capacitance and resistance are actually hindering things. CAT5 cable was also designed for LAN use, not really for telecommunications. It meets all of the specifications for those networks, but these aren't the same specifications used by T1 technology.

T1 circuit technology was developed more than half a century ago and trust me, these circuits can function just fine over "CAT Zero" cable. Category ratings weren't even developed until the 80s. In prior years, cables were just referred to as 'twisted pair' or not. Telcos terminate their circuits on these cards in order to ensure that despite many thousands of feet of questionable cable, they will meet specs at their jack and not another foot farther. Those network termination cards work miracles in cleaning up any errors that may occur in the outside cable feeding them. In a perfect world, and if it was possible, this card would be installed directly in the customer's suite. Knowing Verizon the way I do, we know that's not likely to happen.

Don't forget that Verizon isn't in a big hurry to make their competitors look good, so they aren't going to jump through hoops to take care of what in your case is a stepchild. The best thing that you can do is to do the best you can on the CPE side of the termination and hope for the best. If you really want to play it safe, get a pair of media converters for T1 circuits and run the extension with a pre-terminated fiber cable.

Thank you all for your valuable input. The reason I asked the question is because rain has been given reason for an outage on several occasions I am told. But I see fiber optic equipment and electronics and I traced the cabling and equipment back to fiber optic. I say to the customer 'no, all on fiber, rain should not be an issue'.

The Cat5 extension could be 100 feet, maybe more, and I suppose that is a possibility the phone company equipment does not account for that. From the 'smart jack' there is Cat5 extension to Adtran TA916 so I believe the Adtran could boost the T1 signal as well, if that is the problem, but it all belongs to the telco. This is all tough to troubleshoot and it's been passed over by many others so it's an opportunity! Thank you and I've always enjoyed this board!

Ed, thanks for the history lesson. Well explained

Verizon would almost definitely have put in an an adtran 3000 shelf to turn an oc3 signal into multiple t1s, if they did anything like that at all. Please google for a picture of that. They might do that if the density was high enough at one point

The glass front shelf with multiple t1 cards is not necessarily fiber fed. That would be typical in a high density terminal room, which sounds likely since you said you got 300 pairs terminals.

'Rain' is not acceptable excuse for an outage. You have a t1 with a service level agreement, they gotta fix it. Your provider sounds like garbage. Shop around.

You got the benefit that they will condition a new copper pair to feed the new circuit as long as your old one is still active.

https://www.bing.com/images/search?view=detailV2&ccid=9RQq2nI2&id=EC03F8C797C5913AB3AB0E1C56C0021B33D38B93&thid=OIP.9RQq2nI2oaIWgnofM91CtQHaEO&mediaurl=https%3A%2F%2Fs-media-cache-ak0.pinimg.com%2Foriginals%2F95%2F81%2F9d%2F95819dc89493a4aadea0e0f54cbd1f1f.jpg&exph=1624&expw=2851&q=adtran+ta3000&simid=608005538963457795&ck=021DF1F33360E1A37878B45A00C602AC&selectedindex=0&pc=EMMX01&adlt=off&shtp=GetUrl&shid=3ef4b403-f72e-4018-b2e4-46a722f5d1b9&shtk=QWR0cmFuIFRBMzAwMCBEUzMgTXVsdGlwbGV4ZXIgZXF1aXBtZW50LiB8IFRlbGVjb20gfCBQaW50ZXJlc3Q%3D&shdk=Rm91bmQgb24gQmluZyBmcm9tIHd3dy5waW50ZXJlc3QuY29t&shhk=4cYt5SoAHiMsLB1XaRK1Vo3ecVAWd1QCXAvhsbCRvC4%3D&form=EX0023&shth=OSH.RafbeNUMua7Z4lzKx%252FZ27w

They make another one that looks very similar is about half as tall and is still called TA3000