Shocked jocks' O2 calls crossed with Brummies, now everyone's cross
No crappy crossbar to blame either
O2 customers in Birmingham have been listening in to callers in Scotland with the kind of crossed lines not usually experienced on a telephone network for decades.
The problem isn't widespread, but O2 has confirmed that customers around Birmingham have found themselves lurking on Scottish calls in an unrequested party line, able to listen in to what should be private communications without the knowledge of those making them.
Reg reader Phil Armstrong told us about the problem on Friday, having reported it to O2, but the operator wasn't able to confirm the existence of the crossed lines to us until after the weekend and even now admits to being unable to replicate the problem despite having received "a handful" of complaints.
Crossed lines get their name from the first automatic phone networks, based around a "crossbar" switch. Connections were established using a frame with two layers of parallel wires, giving the appearance of a grid when viewed from above but actually just apart from each other. A hammer at each cross point could push the wires together, making an electrical connection, and banks of such frames connected phone calls.
But two hammers pushing two intersections with only one intersection between them could create a contact at that point, a "crossed line", connecting two separate calls into a single party line.
It seems very unlikely that O2 has been running its network over networking kit approaching its centenary, entertaining as that thought is, so the problem here is obviously more digital in nature but it seems a good deal harder to track down.
Reports of similar problems on O2 go back to 2010 at least, pointing to some long-term but very rare problem that flares up every now and then. O2 say it'll update us when it can, but in the meantime anyone discussing assassination plans or dead-drop locations should stay off O2 especially if they're in Scotland. ®
Crossed lines get their name from the first automatic phone networks, based around a "crossbar" switch
Nonsense, crossed lines predate crossbar switches by at least 20 years, and probably longer.
There were a number of reasons why you would be able to overhear another call. In the early days of paper and lead insulated cables, (still in use in the 70s and 80s) you could end up with cross-talk between pairs if the cable got wet.
For actual interconnection of calls, these could be caused by the operator plugging a call into the wrong jack, and later, on Strowger exchanges, they could be caused by the wiper stepping to the wrong contact due to relay stutter.
Fortunately we don't ever get crossed lines on the Internet because of the annual cleaning day:
Crossed Lines Too Many Causes to Number
I am sorry but crossed lines well pre-date the use of cross bar and other 'modern developments'. They could be caused by dropped solder on jumper frames, un-recovered wiring on jumper frames and other inter tag bridging on the frames. Then there were the mechanical issues, broken 'P' wires on switches, faulty wipers bridging, crossed joints in cabinets or joint chambers and so on, then there were the issues of water ingress and a few times deliberate actions, think illegal home made wire taps. This 'wonderful' variety made it so 'interesting' to fault find.
Modern switches such as cross bar and some, (probably more than 'some') digital switches introduced their own twists on the crossed, i.e. unwanted multiple connections. All of these could be either one way 'taps' or both-way 'taps' allowing both parties to be heard. Some times the 'added value' could be free of charge and sometimes not...
Of course some of these caused service loss, so you might only be able to listen into other people's calls when you would probably have more incentive to complain. In other cases you might never get the same callers twice.