What does the term "house pairs" refer to in the industry when speaking about a DMARC extension.
Thanks guys (and girls).

There is a hierarchy of telephone cables and pairs in subscriber (exchange) service. Starting at the central office (CO) and extending all the way to the subscriber: (F stands for Facility)

F1 = Feeder pairs = cable pairs from the CO to the main distribution box in a block or in a large building.

F2 = Block pairs = distribution pairs in cables that might be run from the above main neighborhood terminal box to other subsidiary terminals in smaller buildings. Sometimes these are referred to as "aerial" pairs, because historically, feeder cables run underground, either buried directly, or in ducts, and emerge a few miles away from the CO to become aerial cables (on poles).

F3 = House pairs = cable pairs that run vertically from the basement terminal in a building, up through the floors of the building to smaller terminals (typically 11-, 16-, 25-, 50-pair) located in hallways or utility rooms on each floor.

House and local cables form the (permanent) distribution infrastructure in a building.

F4 = Local pairs = sometimes there is another subordinate cable from the house box to another smaller box on the same floor. These pairs are called "local" pairs and are horizontally run.

The final IWC (inside wiring cable) pairs that get a subscriber's dial tone to their apartment or office are run from the house box to the premises by the installer. In these cases, the NID (DMARC) is supposed to be inside the premises, but there are exceptions to this rule.

Most of this is historic POTS terminology and has been superseded, in part, by PANS. For instance, some F1 pairs (feeder pairs, as explained above) are now created out in the country, having been derived from copper- or fiber-fed SLiC cabinets (Station Line Carrier) which are multiplexers.

The term "house cable" was generally referred to as riser or distribution cables that were installed by the telco to extend their services to each floor or area of a building.

In high-rise buildings, for example, the telco would run a 1,200 pair cable up from the basement and tap into it at each floor to provide, say 100 "house" pairs. At the time when these cables were still owned by the telco, they maintained responsibility for the lines or circuits to that particular floor's telephone closet. When they owned (and rented) the phone system, nobody outside of our industry ever heard this phrase. The house pairs used for a circuit were actually documented as a part of the circuit route. For example:

A circuit left the CO on a cable pair, let's just say "cable 236, pair 1354, BP (binding post) 154" at the local cross connect box. This is referred to as an "F1" (Facility, or field segment one) pair.

At the cross-connect box, this pair was then connected via a jumper wire pair to a pair in an outgoing cable that serves the immediate area of the building. This would be referred to as the "F2" segment, say pair 809 in the cross-connect cabinet.

Once this pair terminated at the building's main entrance point; there may only be a 25 pair terminal that contains F2 pairs 801 through 825. This is referred to as the "terminal address" (TA). The building down the road may contain a 100 pair terminal that contains pairs from this same F2 cable, pairs 826 through 925.

This F2 pair now becomes F2 pair 809, BP9 because it appears on the ninth binding post pair at the building's terminal.

From there, an installer would again cross-connect the circuit from BP2 (F2/809/BP09) to an available pair in the house cable to reach the appropriate floor of the building. This third cross connection was often referred to as an F3 segment. An available pair to the fourth floor was found to be pair 477 of the house cable which appeared in the fourth floor's house count of 401-500. This 77th pair of the floor's house cable count ends up on BP77, since the floor's BP count is 1-100.

So, for cable plant records, this circuit would be recorded like this:

F1/CA236/1354/F2/809/TA/BP09/F3/477/BP77

Pair 477 is the "house" pair, since it only exists within the building, or 'in-house'.

After divestiture of the Bell System, where most other telcos followed-suit, the telcos abandoned ownership of these house cables and documented F3 assignments, yet they retained the terminology.

This terminology remains to this day, however it only means something to someone who has been in this business prior to the 1980s. Telcos today can't even be paid to install and maintain house cables. They don't want the responsibility for a circuit any further into a building than necessary.

It's just a matter of time before they rally to limit the responsibility for their circuits to the nearest pole, pedestal or manhole.

Was that explanation clear as mud? Yes, I know. There was a much easier answer.

EDIT: Arthur beat me to it.

Thank you so much.
Greatly appreciated.

For me, as a business owner---when we can use house pairs---we save ourselves a lot of time and we save the customer a lot of money. However, most technicians these days don't understand how house pairs are run---therefore---most of the time can't even use them. I'm lucky, I have a head installer/tech with well over 45 years in the business. He knows how the cable is run in most buildings around here--and where the IDFs (intermediate distribution frames) are.

We have to chuckle when we see guys running 5 or 6 cables (4 pair)---because they have no idea how to trace the house cable pairs. We chuckle---but it's sad. In ten years there won't be anyone around that knows how to trace cable. It's almost a lost art now. I wouldn't even attempt to explain what "house cables" are to most IT guys. They would just look and shake their head.

Thanks for the explanation Arthur and Ed. I often times see the plant codes written with permanent marker inside the NID. I figured it meant what cable, bp, etc but didn't know how to read it properly.

Happy to assist, Hawk. As you can obviously tell, some of us here are very passionate about this stuff and I consider OSP cable practices to be one of my specialties.

I know what you mean about markings on terminals. Keep in mind that a single building terminal may be served by pair counts from several different cables. That is where the fun begins. I imagine that you've seen markings like this before on a typical 100 pair BET:

CA54; 601-625 BP 1-25
CA102; 1251-1275 BP 26-50
CA91; 1876-1925 BP 51-100

This often occurs because the customer demand exceeded what the telco originally expected for the building and the local demographics. (They put a lot of thought into planning for this stuff). Still, they never know when some telemarketing group might set up in a building in an industrial park needing many more lines than the area's typical auto shop might demand. They end up having to steal binders of cable pairs that might have been allocated for other areas that just happen to be available to share.

This "stealing" of cable pairs may occur miles down the road where they have to tap into the resources of another cable.

Have you ever been driving down the road and looked up to see two parallel aerial cables with splice cases at a pole where a smaller cable jumps between them in horse shoe fashion? That is because they are stealing available pairs from one cable to replenish pairs needed in another.

This really, really gets challenging in areas served by independent telcos that didn't have the "Bell budgets" for cable construction. They would often end up stealing partial binders or even worse, picking and choosing pairs to throw toward the service address. While not the norm, it wasn't uncommon to find individual BPs in a termial with pair counts from different cables!

Those days are gone. Telcos aren't about to go around knocking open splice cases in the air or in manholes to redirect distribution assignments. If it doesn't work, as in most Verizon instances, they just suggest to the customer that they seek the services of a CLEC that can get by with only one pair that is already in place. I can't say that I blame them.

It's a sad state of affairs, to say the very least.

Ten years ago, no one - and I mean no one - would contemplate splitting a block/house/PL pair on a data circuit...

I get to see this type of nonsense more and more often. In midtown Manhattan, no less, where many of the businesses we serve dish out more for a monthly rent and basic expenses than I earn in a year.

Better yet, I got questioned more than once on why I refuse to go along with such an upside-down practice...

As for the "house pairs"...I'd rather have a congested feeder box, than a bad house count. The splicers will eventually come and clear a pair in the main feed... If I need one in the house or riser...God help that unlucky customer...

Things work a bit different in my service area, however I'm not a CLEC agent so it might appear the same to anyone looking in.

I just wanted to say thanks for explaining that terminology. There are (I'm sure) IT guys who don't know much about telecom, but this board and people such as everyone here has helped teach many of us things we didn't really know.

How do the US telco's do Centrix if they don't install or maintain HC or the iwc drop from the floor closet to the cubicle?

Centrex is just a feature package that is added to a group of lines. The customer is still responsible for the routing of these lines to the final destination within the building.

Different from here in Manitoba where the telco still has the house cables and IWC in major buildings.

The customer has the option of buying the end set on their own or from the telco.

We still maintain legacy Centrex lines for the fire department, hospitals and so forth...

I have *never* installed a single one, though, which has to tell you something...they are most certainly going the way of dinosaurs, at least in my neck of the woods...

BTW, I've got a fire department right around the corner from the CO, and blocks upon blocks of major hospitals three minutes away...and I'm talking in terms of walking distance...and all I've ever done was repair these poor oldies... :confused:

fair amount of Centrex being used here, no special lines for it tho. Same copper pairs.

We have hundreds of pairs of old Ohio Bell house cable still in use in our office/plant. Even has the 'inventoried' stickers on it.

I was referring to old-time-dedicated Centrex loops, the usual code is 96CLNA****** in my neck of the woods...and yes, they most certainly do run on the same decrepit copper pairs...