larry@uunet.uu.net (Larry Lippman) (03/18/91)
In article <telecom11.210.4@eecs.nwu.edu> john@zygot.ati.com (John Higdon) writes: > This talk about the problems in Rochester reminds me of a telling > situation that happened right here in my neighborhood a couple of > years ago. > Almost simultaneously the cable, ALL of my phone lines, and the > electricity went dead. A short time later, fire engines were screaming > down the street. It seems that some trees had caught fire in the next > block and had taken out all the services on the poles nearby. > [details deleted] > What is interesting is the order in which the services were restored. I don't see anything surprising here, as I will point out in detail. > Within a very short time after the fire was extinguished the cable was > restored. I have some battery operated TVs and was able to observe > this for myself. There are one, or perhaps two aluminum-sheathed coaxial cables involved. The necessary splices for two coaxial cables can be made in less than ten minutes, with the greatest amount of time being that required to get the ladder in position. Lashing say, twenty feet of new of coaxial cable would probably not require more than half an hour. > An hour or so after that, the electricity came back on. No big deal, either. My guess is twenty minutes per individual primary or secondary conductor per pole span, and/or sixty minutes per pole span for new triplex with one or two service drops. > As it turned out, telephone service was restored by late afternoon, > about twenty-four hours after the outage began. Not very impressive. I suspect you may be rather harsh on the local telephone company. Since you have not described the type of cable or estimated a pair count (which I suspect you probably could do), I can't give a really specific response. However, I'll address a few general issues. First, in the case of damage to a telephone cable, it is necessary to cut out an entire defective section, and replace it with a new section of cable which must be spliced at *both* ends. If you had a 100 pair cable, one would have to splice 100 pairs at one end of the section, and 100 pairs at the other, for a total of 200 pairs or 400 individual wire connections. If it were a major feeder cable, the pair count could be 200, 400, 600 or more pairs - multipled by two for the number of splices. While much cable splicing is performed using multiple splices that splice 25 pairs at one time (like 3M MS2, WECo 710, etc.), instead of the traditional one-wire B-connector or 3M UG connector, such splicing still takes time. The last thing that any cable splicer wants is to go back and open up a splice because of a split or transposed pair. The worse possible scenario is that the damaged cable was lead-covered pulp insulation. Ever see the color coding on a 101 pair pulp cable? You have fifty pairs of white/green, fifty pairs of white/red plus a red/blue tracer pair. Repair of such a cable requires identification of EACH pair from BOTH the CO end and the subscriber end. Consider how much labor is required if say, you had a 404-pair or higher pair-count pulp cable. The cable in question may well be pressurized; it certainly will be if it is a pulp cable. Repair of damaged pressurized cable usually involves building a "pressure" dam at each end using epoxy cement, along with creating a pneumatic connection to temporarily purge the cable with dry nitrogen. Pneumatic continuity is later restored when the splices are complete. Sheath preparation of aerial cable requires care in order to maintain a low-impedance grounding path, in addition to any sealing requirements if the cable is pressurized. Following a cable break, the first thing that a telephone company will usually do is check their outside plant records to see of any emergency services or special service lines are affected. If *justified*, "restoral boards" may be set up at both ends of the damaged cable section to effect temporary continuity for critical pairs. Using a restoral board approach, critical pairs could be temporarily restored in a few hours; the longest delay is searching plant records and getting pair identification data to the field. Placing restoral boards crowds the damage site and significantly prolongs the repair and splicing process. Ain't no way that restoral boards will be used for POTS pairs. If many pairs are affected, a craftsperson in the CO may pull the protectors to open the circuits and clear any potential permanent signal alarms. Following the cable repair, the protectors are then replaced to restore service. All of the above takes *time*. My guess is that a two-person crew can replace a 100 pair cable section in about six hours if the cable is PIC and unpressurized. A four-person crew can reduce that time by about one third. A longer time is required if more than 100 pairs are involved, but it is not a linear relationship since certain common work must be performed regardless of the number of pairs (i.e., a 200-pair cable may require only 20% more time than a 100-pair). If the cable is pulp, all bets are off. A well-utilized 101 pair pulp cable may well require fifty or more labor-hours to repair due to all of the necessary identification procedures. > The cable company had its act together. Its service restoral (while > hardly essential) was first rate. Give me a break. Their repair effort was absolutely trivial by any reasonable comparison! > PG&E took three hours to restore service. PG&E is probably the worst > electric utility on the planet so for them it was probably miraculous. Sounds about right for one pole span. No big deal here; one visually matches a few wires. Not even any color codes to match. :-) No checking of plant records is even required (except to identify any life-support locations). > But wiping up the rear was Pac*Bell, who was too wimpy to even > begin work on its cable until the next day. First of all, unless there is some dire crisis (sorry, but POTS service does not qualify), a telephone company will generally not work on aerial cables while the electric power utility is still working on the same poles. This is just standard safety practice in the telephone industry; I'm sorry if you think it's "wimpy". The fact that the CATV company completed their repair before the electric power utility does surprise me, however. Replacing aerial cable during nighttime hours (which I assume we have here) is a very undesirable situation due to the difficulty in obtaining good site illumination. Yes, I know there are such things as flood lights, but the attention to detail necessary for telephone cable repair work is orders of magnitude greater than for electric power lines. If solely POTS subscribers were affected, and if the damage occurred at night, in my opinion a reasonable "value judgment" on the part of telephone company outside plant supervision would be to wait until morning. So, let's say damage occurred at 7:00 PM, the electric utility completed its work by 10:00 PM, the telephone company elected to repair on the day shift, and one shift was required to effect repairs, the overall time to restore service may well be 24 hours. While you may not be very happy about the situation, this is just a fact of life. Larry Lippman @ Recognition Research Corp. "Have you hugged your cat today?" VOICE: 716/688-1231 {boulder, rutgers, watmath}!ub!kitty!larry FAX: 716/741-9635 [note: ub=acsu.buffalo.edu] uunet!/ \aerion!larry
wb8foz@mthvax.cs.miami.edu (David Lesher) (03/19/91)
{John and Larry discuss a fire damaged cable repair}
I have to side with Larry on this one. Pre-breakup, I was in charge of
35+ leased pairs of various types into a facility. While outages on
one or two was a regular daily occurance, one night at midnight I got a
frantic call from the shift operator.
He was on the last of four POTS lines, and the ground on one side of the
pair was VERY obvious ... he reported that he had a board full of
failures, and both (60 ma. loop) ASR-28's were "running open," too.
I quickly (before the last pair died - a few minutes later) reminded
him to use the 156 mhz radio as needed, and had him drive down the
cable route to find the problem. He called me on the air to report a
tool shed on fire under the trunk.
Through some miracle, I got the 611-droid to wake up the Cable foreman
for the area. After several attempts, I got the one for the correct
district ;-}. (The others went back to sleep.) [If you REALLY want to
know - it was the 28 cable in the Shadyside CO]
I went out too, and Ma *did* start on the repairs after the power
utility got the 13.2 kv and 230 v stuff fixed. It was a real mess. The
fire had been at a corner pole, and had wiped out a splice cap, too. A
four man crew, or maybe more, worked until late that afternoon. It was
a little easier, I recall, because my repeated harpings on failures
had at least forced Cable to keep the records up to date;-}
What you REALLY want to do, John, is just get a SLC-96 installed in
your basement ;^]. Then, next fire, all they would have to do is run
some new fibers.
wb8foz@mthvax.cs.miami.edu (305) 255-RTFMjohn@zygot.ati.com (John Higdon) (03/21/91)
David Lesher <wb8foz@mthvax.cs.miami.edu> writes: > What you REALLY want to do, John, is just get a SLC-96 installed in > your basement ;^]. Then, next fire, all they would have to do is run > some new fibers. Well, I tried to get T1, but even when it becomes available, Pac*Bell wants to charge me extra to save them money. Right now, my ten lines come in on individual drops, reminiscent of an alleyway in some slum. My friends all have managed to get Pac*Bell to at least install cable drops to THEIR houses. When a repair type comes to the house, he has to pull the covers off of every type of protector block available over the past thirty years to find the line in question. I would love to get it cleaned up, but it is on Pac*Bell's side of the demarc and you can bet there is no interest whatever in cleaning anything up. Especially at MY house :-) John Higdon | P. O. Box 7648 | +1 408 723 1395 john@zygot.ati.com | San Jose, CA 95150 | M o o !