mm wrote:
On Thu, 15 Feb 2007 00:13:13 -0600, Jim Redelfs
wrote:

In article ,
mm wrote:

Did dial-up ever cause a shortage of phone lines?

Lines? Yes, in some places.

Switching capacity? No. Subscribers "camped-on" for hours and days and we
never broke a sweat.

In the switched phone system, staying on the phone for long periods
does indeed affect switching capacity and calls being very long
doesn't solve any capacity issue. In fact, it makes it worse.
There is some overhead in getting the call setup and then taken down
again, but once established, there is no more overhead. The call
going from your phone to someone elses now just involves constantly
taking the voice sample from your line card in the central office and
putting into timeslot 25 and then the line card serving the guy on the
other side of town taking the voice sample from timeslot 25, turing it
back into analog and sending it on the wire to the guy's house.
That process, once set up, is fixed in hardware contained on each line
card. Once told what time slot to look for, the line card is just
counting timeslots, which are like a digital highway, as they go by.
One card puts it into timeslot 25, the other takes it out of 25.
There is no more CPU, software, etc involved.

So, if it's said a switch has run out of capacity, it usually means
that there isn't enough slots to plug in more linecards to handle more
lines. It's also possible that it could run out of timeslot capacity
to connect all the physical lines, because I don't think they
necessarily have capacity to handle having say all 10,000 lines in
service at the exact same time. But the point is, whether they run
out of capacity is a function of how many lines have calls going, and
not how long the calls last.






Hmmm.. I wish I had known this earlier. I woulldn't have gotten off
the line.

BTW, I quote myself when I don't want my comments to follow someone
else, when I don't want to look like I'm arguing with someone else. I
do enough of that anyhow.

Thanks to all, and especially you for clearing things up, and trader4
especially for his second post which cleared things up.

This is one of those questions I've wondered about for year.s

What follows was interesting too.

A lot of people have gone to cable now, but there was a period were
20, 40, 80? million people had dial-up and they stayed on for hours
and hours, maybe all day.

Never a problem. By the time dial-up internet was at its peak, virtually all
switching systems were digital. Most interoffice connectivity was (and is)
via fiber optic cable.

Cnversely, is there now a lot of excess capacity on phone-only lines,
now that many people have switched to cable?

Not a lot. The biggest factor idling ILEC (Incumbent Local Exchange Carrier)
pairs was loss of customers to CATV getting into the dialtone business. It
was (and is) a *HUGE* loss.

Doesn't even switching to DSL end up using new central
station hardware

Yes.

leaving old phone-only hardware unused?

No. The existing "phone-only" equipment is still used. Additional equipment
is ADDED to the loop to enable DSL service.