atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services Outside Plant OSP Construction Qwest pair counting?

I just stumbled upon this because it was the newest thread...never been so confused about pairs of wires
anyone care to put this in layman's terms for your favorite rookie

Sorry Jeff, didn't mean to confuse ya. Odds are you will only deal with straight counts, 1-whatever. DEMARKs, even big ones should be labeled. Telco cable count can get confusing, if you've never worked with it. A cable leaves a CO with a cable number and count, 01-1-600, means cable 1 pairs 1 to 600. As you get away from the off these cable break off and go different directions so each one that breaks off gets it's own, or they can multiple of the same count. So say one cable breaks off and is a 50pr cable and gets a count of 01-551-600, now that cables pair one, bl/w group w/bl pr is pair 551, might be pair one in the sheath, but it's pair 551 of the cable count. I'm not going any farther, cause they break off more from there, then you get to the cross connect points and everything changes, only now it's not a CO count out of the cross connect box, that's where you get the F2 term from. Clear as mud? Maybe Ed can explain it better. Us old splicers seem to make easy things seem hard. :rolleyes: :confused:

Jeff: You better not be messing with me because I am going look like an idiot in trying to be serious in answering your question if you are...

Telcos try to provide plenty of spare pairs at every address or at least nearby at a pole- or pedestal-mounted terminal. They don't want to have to bury another cable each time a customer orders another line.

In a perfect world, there would be a clean 25 pairs from each local terminal back to the central office. Common sense says that if all 25 pairs from all of the terminals in the community came back to one place, there would be millions of wire pairs. Far too many to maintain and terminate at the CO, and a tremendous waste of space or resources.

There are many different names for the topology that was developed to handle this situation, but I will use SAC (Serving Area Concept) for my example:

While it's true, one customer may only need one pair while their neighbor may need five, there's little likelihood that many subscribers in a particular area will need that many pairs. Telco plant engineers have formulas that are used to estimate pair requirements. Most residential areas are planned for maybe 2 pairs to be active at the most. They also have to calculate a certain number of spare pairs to permit rapid service restoration in the event of a damaged pair. That being said, it makes more sense to provide for plenty of extra pairs to each address, (F2 pairs) like with 5 pair drops to each one, but to have them all terminate at a local point instead of going all the way back to the CO.

This is where a SAC cabinet (cross-connect cabinet, B-Box, there are many different names for them) comes into play. They are either pole or concrete pad-mounted and resemble a typical splice pedestal, but larger. Some big (3,600 pair+) ones have doors on both sides. They are usually located near the entrance to a neighborhood or business complex, but they can show up anywhere depending upon telephone circuit density. They are usually pretty easy to identify because they are larger than a typical pedestal and you will see technicians working in them pretty regularly, even in just a residential environment.

Within these cabinets, most, if not all of the local (F2) pairs are terminated on the blue, or "field" blocks. They can be 88 blocks (similar to 110), screw-terminals or newer insulation-displacement connectors (IDC). Some older ones actually still use 66 blocks or hex-head binding posts, but they are quickly being phased-out.

Since there's not likely a chance that every single field pair will need to be active, a proportionally-smaller feed cable (F1 pairs) feeds this cabinet on the green or "CO" blocks. In a typical 2,700 pair cross connect cabinet, there are 900 incoming (CO/green) pairs and 1,800 outgoing (field/blue) pairs. These in/out ratios can vary depending upon the installation.

The bottom line is that this is a simple weatherproof cross-connect field. Just like running a 25 pair cable to feed ten four pair station runs. You won't likely use all four pairs in each station cable run, so it's safe to assume that a 25 pair feed is enough. It's a safe gamble that telcos make every day using cross connect boxes under a serving area concept.

This concept also permits point-to-point circuits to be created between local addresses (F2 to F2 pairs) without having to reach all the way to the CO and back again (F2-F1-F1-F2). Telcos don't like to do this because it makes is difficult to troubleshoot without rolling a truck, so these local circuits are not very common.

So, in closing, the original question stemmed from pair numbers not necessarily matching pair colors, so here's how it can happen:

1) Your new second line, 867-5309 leaves the CO on cable number 243 which heads out in your direction, pair 1943 (yellow-green). This is an F1 pair.

2) The cross connect box located at 3rd and Maple is fed by a 300 pair branch from cable 243, pairs 1801-2100 and your pair is included in that count.

3) A 1,200 pair F2 cable leaves this cross connect box and feeds 10 and 25 pair terminals on every pole in the neighborhood.

4) There is a ten-pair terminal on the pole in front of your house is fed by F2 pairs 601-610. Pair 606 (red-blue) is determined to not be in use.

5) The second pair (white-orange) in the buried drop to your house is connected to the F2 pair 606 at the pole. The drop is terminated on a NID and usually, a toner is connected.

6) Back at the cross connect box, the installer
traces their tone down to F2 (blue field) pair 606 and verifies that the pair is good. They usually do this because records on F2 pairs aren't usually well-kept.

7) Once the F2 pair is confirmed to be good to your house, they locate and confirm that your new number (867-5309) is working proplerly on F1 pair 1943. Once this is determined, a jumper is placed between the F1 and F2 pairs.

Summary: Cable 243 (F1) Pair 1943 (yellow/green) connects to F2 pair 606 (red-blue) that connects to drop wire pair 2 (white-orange) to complete the circuit.

8) The installer forgets the toner that they left plugged into your NID and you win a prize when you go to connect your inside wiring.
:rofl:

well said ED, but you forgot about when the installer takes lunch, gets a few in him :toast: , cross connects your new number to someone elses exsisting service and you have cross talk for a week.
:scratch:

Ed-
I was completely serious. Thanks for the information.
Anthony-
That sounds about right

Glad to help, Jeff. I hope it made sense without boring you to tears. By the way, Anthony, your follow-up was a classic! You forgot to mention the five calls to repair service where they politely remind you that "if the trouble is found to be in your inside wiring, there will be a charge".

Maybe the repair clerk had "lunch" with the installer.

Yep, youz guyz are a riot --- 3 martuneeees lunch --- do you know how many martinis it takes to fill a green olive bottle? One martini at a time?

Jeff, think of a cable count like a sky scraper --- heavy and wide at the bottom and after some ways it gets smaller and after a ways further smaller again until there is nothing left but a little area on the roof.

When it leaves the CO it is big (say 1200 pr) then breaks down to a 900 pr then a ways further to a 600 pr until it gets to yet another break down to 300 pr then a ways on it may be a 100 pr and then a 50 then a 25 and finally a single pr drop into your house.

I could always find the CO in small towns with pole mounted cable ---- the bigger it got the closer to the office.

Just a generalization, not a text for a copper splicer.

KLD

That's funny that you mentioned the "looking for aerial cables getting larger in small towns".

I still find myself doing that all the time. What's funny is that you will see three enormous (2,700 pair+) cables converging on a little brick building the size of a storage shed! If it wasn't for the Verizon, GTE or Bell Atlantic plaque on the door, it probably would be assumed to be a shed. Probably pretty cozy inside.

The giveaway is the fact that it's the only shed in town with a generator and a paved driveway!

I was going to mention that. My personal favorite is "the static is being caused by your cordless phone"....ummm I am calling from you nid with nothing else connected"......"Sir please unplug your cordless phone"

Classic

There is no F1 on the loops I'm ordering. We put our own DSLAM next to the cross box and order cross connects and F2 from our equipment to the customer premises.

We had another one on Thursday that wouldn't even pass a toner through it. It was on 1627 in the cross box on the distribution side, allegedly on pair 4 on the building cable. There is a 200 pair service to the building. Pair 2 on that same block was 1/2 of a T1 that wasn't in alarm, so I don't think that was my pair.

In the area that is causing most of my pain and insanity all of the buildings have multiples of 25 pairs for the service to them.

dave