T-1 termination

[richjo]

How is a T-1 line normally terminated by the Telco at the demark (network interface)?

Is it terminated on a punch block or do they run it to a jack?

Also, which pairs are used for what (the transmit receive) on the punch block or in the jack?

I need to cable it from the demark to a RJ45 jack & then patch cord it into the router.

I'm suppose to extend a demark for a T-1 & hook up a router & I have'nt worked on T-1 lines before. :roll:

THANKS

 

[El0him]

They normall terminate it on a smartjack. T1s are essentially a RJ45 with with the same pinout as a EIA/TIA 568A/B pinout except the electrical pins are totally different so you cannot plug it directly to an ethernet interface. You will need a T1 CSU/DSU on your router to plug this into. If you don't have any internal CSU/DSU on your routers than you need to get an external CSU/DSU in which case you will need some V.35 interface on your routers.

 

[richjo]

Since I posted this I talked to the "help desk tech guy" that supposedly I am to call from the site.

He said that the telco wires it thru "some electronics- a grey box" & then terminates it at an RJ45. He said that this can either go to the router directly or I need to extend this.

Could this 'grey box" be the "csu/dsu"?

 

[El0him]

No it's a smart jack... Providers rarely put CSU/DSUs out because they don't know what your application is. I mean, you could be using it for an FXS/FXO application. The smart jack is nothing more than a jack that has the capability to loop when it detects that there is nothing plugged into on the RJ45 side.

 

[fredweston]

That's absolutely correct. You need to take a normal Cat5 cable and connect it from the smartjack to your CSU/DSU. Any modern router will usually have an integrated one, or at least have a slot for one. A WIC-1DSU is for a modular Cisco router such as a 1700 or 2600 series. Check out the picture, that's where you connect the other end of your Cat5 cable.

If you have an older router such as a 2500 series Cisco, with a serial port that looks like... a serial port, then you will probably need an external CSU/DSU.

Keep in mind that when you set up your CSU/DSU (or configure the router if it has an integrated CSU/DSU), you'll need to configure the appropriate framing/coding and which timeslots to use. For example, if you have a fractional T1 with 256kbps then you'd normally use timeslots 1-4 (4 x 64kbps), but some providers like to be difficult and use 21-24 or 15-18. This would be easier if we knew what type of router you had.

 

[richjo]

OK

It's starting to make sense---lol

As I went back & looked over the .pdf 'job info' that they gave me & there was the info for the internal WIC card.

So is the demark extesion patch cable wired for A or B sceme?

I have to run this to a RJ45 jack at the router location.

Thanks guys!

 

[fredweston]

It makes no difference, just make sure both ends are pinned the same.

 

[El0him]

Doesn't make any difference whether its 568a or 568b... just make sure both ends are 568a if it's A and so forth.... if you got a cable that is 568a on one end and 568b on the other then you got a crossover cable. The only difference between the two as far as I can tell is the color coding.

OK

It's starting to make sense---lol

As I went back & looked over the .pdf 'job info' that they gave me & there was the info for the internal WIC card.

So is the demark extesion patch cable wired for A or B sceme?

I have to run this to a RJ45 jack at the router location.

Thanks guys!

 

[fredweston]

Yeah a X-over is A on one end and B on the other. Basically pins 1-2 and 3-6 will be switched. A & B are just best practice standards. They make more of a difference if you're dealing with an RJ-45 on one end and something like a 110-style block on the other end, because you can't just physically look at each end to make sure they're the same in that case. If you have a cable that has the exact opposite pinout like this:

1-8
2-7
3-6
4-5
5-4
6-3
7-2
8-1

Then you have a rollover cable. This is often what you need to connect to a console port on a router.

 

[richjo]

OK--Thanks alot everyone-I think I'll be able to handle it without causing too much damage.

:roll:

 

[Cambria]

Hey guys the difference between a 568a and a 568b is (a) is used primarily in voice applications and (b) is used for data. Either can be used but speeds may be affected.

The unused wires in both schemes are used to shield the active wires from crosstalk.
Since the schemes are intended for different applications, wires are wrap in a twisted format on different wires to shield them, this best to stick with schedule B for all data wiring.

This is also how they achieve the high frequency rates on the CAT5E
from 350 to 500 MHz, they merely increase the twist on the active cables to increase shielding.... as you can see the term UTP (unshielded twisted pair) can be a bit misleading.......


Remember always wire according to schedule, if all you got for data is schedule A
then wire accordingly. It will work but perhaps at a lower rate...better than introducing cross talk!