I shouldn't have used the word "lines". I mean whatever is needed at
the central stations to keep a phone call running.
Isn't that what there is a shortage of when someone gets a fast busy
on a local phone call?
I'm sure some resources are used in addition to my phone and the line
running to my local central station.
What it takes at the central office to switch a local call is a
central office switch. In the US, most common is the Lucent 5ESS, std
version of which handles 10K lines. The switch connects local calls
to local lines, and local calls going outside that CO to digital lines
crossing regions. During the dial up, fax, etc line expansion days,
Lucent made buckoo bucks selling these to handle the new lines. It
was a big multi-million piece of hardware, that was overpriced and
nothing special, but telcos bought em, right and left. It fueled
Lucent's big growth and success in the 90s.
Quoting yourself, I see. There's a treatment for that, ya know. <grin>
You are referring to a "reorder" or circuits busy condition. A busy signal is
60 TPM (tones-per-minute). A reorder is 120.
Getting a reorder is, thankfully, an increasingly rare occurrence. It can
happen for numerous reasons, the least of which is a "shortage of equipment".
Sometimes the call just goes astray and hits a brick wall. Other times the
call is routed through equipment, perhaps in another city, that is
experiencing trouble or extremely heavy usage. Simply redialing the call
usually results in success.
In my small town, yes it was a shortage.
When I was on dial-up, I used a second line. In that part of town I
would get a good 33.6 on it most of the time, with frequent rocket
boosts to 52000.
When I moved to another part of town that was pair-deprived, The Phone
Company put my 2nd line on some mofu digital magic box that gave me 2
lines on one pair of copper. And dropped modem speed to 22000 or 14000
I outfoxed them by giving the 2nd line to the teenagers and getting a
THIRD line - it was not on the magic box and I was back to 33.6/52000
speeds (someone else in the 'hood gave up a pair of copper and got put
on a magic box, heh heh.)
DSL brought speeds topping out at 760 - woo woo. Good for a year until
cable modems came along. After cable voip, I surrendered all phone
company lines back to them.
Hmmm.. I wish I had known this earlier. I woulldn't have gotten off
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.
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.
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