Digger goes through a cable serving many subscribers

[ColinD1]

How does the telephone system recover when a new cable is put in?

Don’t actually know how the damage was done, but started noting oddities. Received a flurry of wrong numbers. Friends were not recognising us from our CLI. Then phoned home from mobile to check and couldn’t get through. Phoned mobile from home and confirmed number associated with line is not my own. Able to phone this number and get through to my landline. 

Fault reported and action being taken. Spoke to the engineer as we are away from home and he gave the information about the broken cable. Will not know if it is fixed until we get home. 

However under these circumstances (of a broken cable) are the pairs just allocated at random and only sorted when people find they receive “wrong numbers” or people cannot reach them? Obviously there are potential problems with call charges being allocated to the wrong person as well as the general disruption. 

[Keith_Beddoe]

@ColinD1 

It depends on how accurate the local cable pair records are, and whether an Openreach Field Technician updated the records when a pair was changed in the past. My past experience shows that this sometimes does not happen.

Its very likely that a number of records are inaccurate, so its probable that crossed line will occur and Openreach would not be aware until customers` complain. Then its gets messy, as each pair has to be proven end to end. This can take a very long time.

Even customers on BT Digital Voice would be affected, if they get connected to the wrong ISP.

[ColinD1]

Thank you. I had done trawl through the internet and it obviously happens with consequent confusion. 
Having had earlier experience with things going wrong I was prompting the call handler with the idea that I could tell her the number now associated with my line. I do not think it is on their script. I presume they always say the fault is in your wiring and insist you go back to the main socket even if you have mobility problems. Still the threat of a chargeable visit!

one might hope they would be proactive in checking. Obviously copper landlines are going the way of 405 line tvs. 

[licquorice]

Done properly, it shouldn't need to rely on any records. The way multipair cables are constructed allows each pair to be uniquely identified by a colour coding system and layers within the cable. Difficult to describe, but simple when looking at a multipair cable.

[iniltous]

Traditional telephony lines use a pair of wires , the underground  cables containing these cable pairs vary in size , but can easily be in the 100’s of ‘pairs’ , for example a cable serving a green street cabinet typically could be a 800 pairs cables .

To differentiates  pair 1 in the cable from pair 800  ( or whatever the cable size) the individual pairs follow a colour code , so should a cable need to be replaced, the new cable can be connected in the same order as the old faulty or damaged one, it isn’t a case that they randomly connect any pair to any other pair and wait for the end users to report issues, however , mistakes can happen , arguably the bigger the cable size the more chance of an error or two , or as already stated , its possible that the cable pair records were incorrect and the new cable was connected correctly but that actually causes an issue, in effect reversing a previous ( unrecorded ) but deliberate crossed pair in the original cable.

There isn’t really a fault ‘code’ for this , someone could possibly report the issue as a crossed line , in effect ‘ I have someone else’s number , and presumably they have my number’  but not all customers service reps would immediately recognise the issue ( they are not engineers after all)  , but once OR are aware hopefully the problem is recognised and corrected.

Once the fault is accepted by your provider, they  advise Openreach who would sort out these errors out, and when your service , and probably the other customer you are crossed with , are restored to normal , then you could challenge any charged for calls that you didn’t make but were made when your line was in effect connected to someone else ( obviously your provider knows the date of the fault report and the date of the fault clear ) and the other person ( who may or may not be a BT customer ) can do the same ( challenge any calls they didn’t make ) with their own provider.
Its not necessarily just 2 lines crossed , it could be any number of lines , but the principal is the same , when the fault is cleared your provider will credit your bill with the cost of any disputed calls upto the date of the fault being cleared , and will probably consider calls made on your account a few days before the fault was reported , as obviously it could be a few days before the issue was noticed…or they may simply make an offer of a credit to your bill , more than sufficient for you to accept as covering any possible losses to disputed calls

[Devon_Dave]

Mmmm Blue, Orange. Green, Brown, Slate

[licquorice]

But it could be or/wh red/grey red/grey red/grey.......................red/grey gr/bk which takes more care 😃😃

[licquorice]

Is my memory playing tricks or was there also a scheme long ago that any new E side cables were correctly terminated at the MDF and then the lengths just random jointed to save time then tapped out and correctly terminated at the cabinet.

@Starwire might know.

[JMB]

I remember years ago when someone cut through a PO cable to a BBC site.  When they went to investigate, there was a workman (not GPO) in the hole twisting wires back together at random.

It was quite normal in the event of the loss of the line for the local PO/BT to ring around to see if anyone had seen any JCBs on the road. In one case it was the Red Arrows who were to blame!

[Starwire]

When I did my Training a long time ago, 20+ years it was explained to us E-Side Cabling was jointed to different Pairs at Cable Joints.

So it would leave the MDF on say Block A101 to Pair 101 going into the CCJ. Then to pair 401 to the External Cable and then say Pair 201 after the next Joint and so on until it got to the PCP.

If I remember rightly it was something to do with Impedance or Noise Balance.

I know when what was then BT sacked off loads of the E-Side Engineers and it all went out to Contract with people like Carillon they just went in numerical order, so A001 to Pair 1 to Pair 1 to Pair 1 all the way to the PCP.

Wasn’t good for ADSL so a lot of the time on SFI and Boost Jobs Openreach Engineers would swap Circuits onto older E-Side Cables as they were usually more Stable.