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and very rarely ever needs repairs, once you fix them." - Dan/Panther

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Central office lines

Started by Phonesrfun, March 30, 2010, 06:28:28 PM

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Quote from: bwanna on March 31, 2010, 09:44:38 AM
i am kind of "jonesing" for telco talk :) thanks for indulging me.

My pleasure.

I will need to digest this a little and I will undoubtedly have more questions.  You know how it goes.  Answer one question and create 5 more.

-Bill G


With respect, I have to disagree with both rp2813 and bwanna, who have theorized that the phone company wouldn't go out of its way, or expend the resources, to serve rural customers. Remember, in those days, the phone company was a regulated utility. One of its primary goals, one initiated by the phone company and enthusiastically supported by the regulators, was "Universal Service" (you can Google this phrase, and Wikipedia has a pretty good writeup). Publically, Universal Service was promoted as a way of bringing telephone service to rural areas where it would not normally reach because of the cost of long lines, and this was true. The regulators embraced this concept, probably rightfully so, and it worked amazingly well. Internally to the phone company, the other purpose was to increase the size of the market, and that was also a legitimate goal.

As part of Universal Service, the regulators approved monthly fees that were the same for urban and rural customers ("IT'S ONLY FAIR"). In urban areas, the monthly fee was higher than the cost of service, and in rural areas it was lower than the cost of service. In essence, urban customers subsidized rural service. The fees were set by the regulators at a level that enabled the phone company to make a regulated amount of profit overall. With a stable and guaranteed income stream, it made sense for the Bell System to expend resources to support the expansion of rural service. Everyone benefitted.

As a regulated utility, the Bell System employed the same philosophy to develop long distance service. Local calls were charged more than they cost, and long distance calls were charged less than they cost. This encouraged the demand for long distance service, and the Bell System responded to the increasing demand by developing the techniques and equipment that made true long distance service possible. Using any other approach,  the development of long distance service would have been delayed by decades. Anyone remember making a long distance call in the 50's, when a long distance call was actually a string of dozens of local calls, temporarily patchboarded together by dozens of local operators? I certainly do. It was awful. And even with the favorable fee structure, it was horribly expensive.

Until the Bell System breakup, this arrangement - regulated service - worked fantastically well, and the phone system that resulted was far superior to anything else in the world. This arrangement also enabled the development of Bell Labs, which was by far the worlds best facility for all things involved in communications. We all know that the transistor was developed at Bell Labs, but we lose track of the fact that a lot of vacuum tubes (including an understanding of how tubes actually worked), as well all the rest of the Bell System hardware, was developed at Bell Labs. The whole concept of communicaitons satellites was developed at Bell Labs, and the first working satellites were built by Bell Labs. Radar was developed and built by Bell Labs. And in addition to these practical applications, , Bell Labs developed almost all of the theory behind communications. A lot of it is pretty arcane, but things like Information Theory and Feedback Theory were developed at Bell Labs. Now Bell Labs is gone, and in my opinion we are worse off for it.

When the Bell System was disassembled, the new telephone companies, being unregulated, came to be motivated by quarterly profit, and the screw-the-little-guy philosophy came to dominate. Perhaps this is appropriate in the modern world. I personally miss the old way.



bill, thank you for your enlightening post. i did not stop to think that pre deregulation days were a totally different animal than today. i will take my 20 lashes (with a wet noodle) for talking before thinking. :-[


Yes, Bill is correct regarding the situation prior to deregulation.  Today's world is a lot different and very much dictated by a combination of shareholders and the bottom line.

Bwanna, correct me if I'm wrong, but I believe that even in the cases where they have "fiber to the prem" the drop from the pole to the house is still a copper pair, no?


The POTS service in our area is pretty modernized. The central office that serves our town is about 2 miles away and it has 2 numbers that serve our town - 922 & 924. I'm in high belief that it's fiber optic all the way up until it hits our neighborhood, there's a nice sized above ground box just down the street that I've seen open before and it looks "high tech" inside for a phone company box...   We also have DSL that joins in to the copper lines to the homes over there as well. When they were retrofitting DSL in, the diggers ended up cutting a cable of 200 or so phone lines and our whole side of town lost phone service... Amazingly they got it back up by late at night AND I got to see them working and talked to them.


ahhhh! ralph, thank you for reminding me about fiber to the prem (FTTP)  there are not any FTTP neighborhoods in the service area i normally work. i do work on alot of FTTN, fiber to the node.

FTTP is offered in new premier neighborhoods. in brand new high$$ neighborhoods the infrastructure is fiber all the way to the side of the customers house. most if not all this is buried plant.

to my knowledge, there are no plans to replace copper & install fiber. i also imagine there is an extra cost to the sub division developer for fiber.

fiber to the node is copper from the node. 3.5k is the approx max distance for a video loop. on 22gg wire you might get the lowest bandwidth signal as far as 4.2k

gus, a 2 exchange CO is relatively small. if you are in a newer neighborhood it is quite possible it is 100% pair gain pairs in the xbox.  a cut 200 pair cable is not a huge project to repair.....a girl can do it :P ;)


I said 200 or so phone lines..... ;D   The cable OTOH was huge, I think they told me something like 400 phone lines it can take, which for this side of town is more than enough cuz it's just neighborhoods over here.
As far as the central office, I'm sure there's alot more exchange numbers assigned to the one by us but the only 2 I know for sure are the ones that serve our town.


the largest cable cut i have ever worked was a 1800 pair pulp cable. the largest i am aware of is 3600 pr.

PIC (plastic insulated cable) is relatively easy to splice, as it is color coded. PULP (paper insulated) has no color codes. pairs have to be tone traced from either end & matched together. very tedious work indeed.  :o



In the situations where the signal will go through one of these gain pairs, like a T1, of course this signal is purely multiplexed data and does not have DC battery or ringing current applied.  At the terminating end in one of these neighborhood cabinets, where the data is de-multiplexed and put back onto a copper pair, can you tell me if there is a 48-volt dc power source as well as a ringing generator in these remote cabinets to insert those needed voltages back into the loop?  If there are, do they have back-up power, or do they go down in power failures?

That would mean that some of the legacy central office functions are actually getting closer to the subscriber. 

Can you comment on that?

-Bill G


attached is a pdf file on pg-flex. one of the older pair gain systems. all i could find on the net right now.

there is power to the RT & yes they do go down in during power outages.
if it is a lengthy outage a generator will be used to supply power. sometimes the customer ends up being out of service for awhile.

later i will look for info on the modern system. i could probably take some real live photos, too if you are interested.

COT stands for central office terminal, RT is remote terminal

i just added a pdf file on litespan (fiber) pair gain


Quote from: McHeath on March 30, 2010, 11:38:25 PM

GPO706 that's a handy little web site that shows the distance from the CO.  Wonder if such a site exists for here in America?

Dont know, typed the old exchange name in a google search and it threw this up, I was a bit gobsmacked.
"now this should take five minutes, where's me screwdriver went now..?"


Quote from: Phonesrfun on March 31, 2010, 12:44:14 AM

That is interesting about the regulator board.  When was it introduced?

Not really a big expert on "bits" them stuff in the phne, but the 706 is the only model I've seen removable boards in, 746's probably had a similar component hard wired and self adjusting, negating the need for the enginner to physically flip the board to isolate it?
"now this should take five minutes, where's me screwdriver went now..?"