Michael Chance wrote:
> The historical telco provisioning models don't have lines available
> for every possible address, since not all of them will have paying
> customers 100% of the time, so they play the percentages and only
> have lines available for the normal load of customers.
I tend to question that. The vast majority of addresses will have
active telephone service and many locations will require multiple
lines. There would be very few lines that might be out of service due
to building vacancy or unable to afford service.
Rather, I think the limiting factor is loop-line-concentrator and
switch capacity. That is, everybody in a given exchange might have a
telephone, but not everybody in that exchange can use their phone at
the same time. I have no idea what the percentage of calls relative
to lines a switch can handle; obviously this varies by community.
(Older concentrators limited the number of active calls within a
specific neighborhood because of line capacity. One critic of the
Bell System claimed Bell was too stingy with trunk lines per
concentrator resulting in unnecessary blocking out.)
(I once visited a #5 xbar switch that had two exchanges assigned to
it. They told me they could handle 60 calls at once, FWIW. It was
primarily a suburban residential area, but it did have a reasonably
sized business district with some large shopping centers and
Now I think cables tend to be built with excess capacity, so a
community having say 250 homes might have pairs for 300 lines or more.
But I don't think the CO is built to put everyone one of those lines
into service -- a dead line that terminates nowhere is different than a
line that terminates into someone's house, in service or not.
> SDT/QDT requires 100% connected lines all the time, and a
> TN assigned to every one of them, with a large percentage that will be
> non-paying facilities that still have to be maintained as if there
> were someone paying for it.
I'm not sure what "maintained" would require. Since the lines aren't
being used, presumably nobody is calling to complain if service isn't
working. Since individual phone lines are bundled into cables and
possibly carrier facilities, if one line has trouble it means a
problem in a cable affecting many people at once. I do agree some
additional work might be required in outdoor terminal junction boxes.
However, I do agree that switching and bookeeping for such lines could
be a nuisance.
I found a demarc box high up on an electric pole in my development, a
red green pair was dangling underneath it. I had no idea why it was
there (the development was old). I didn't try the pair since it was
on a higher voltage power pole and I didn't want to take any chances.
Eventually the pair was gone.