Path: utzoo!attcan!utgpu!news-server.csri.toronto.edu!rutgers!sun-barr!apple!bionet!hayes.fai.alaska.edu!accuvax.nwu.edu!nucsrl!telecom-request From: cellar!martin@bellcore.bellcore.com (Martin Harriss (ACP)) Newsgroups: comp.dcom.telecom Subject: Re: Tracing Obscene/Nuisance Calls in the UK Message-ID: <12127@accuvax.nwu.edu> Date: 13 Sep 90 16:19:39 GMT Sender: news@accuvax.nwu.edu Reply-To: "Martin Harriss (ACP" Organization: Bellcore Lines: 58 Approved: Telecom@eecs.nwu.edu X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@eecs.nwu.edu X-Telecom-Digest: Volume 10, Issue 643, Message 8 of 8 In article <12079@accuvax.nwu.edu> leilabd@syma.sussex.ac.uk (Leila Burrell-Davis) writes: [ stuff about harassing phone calls deleted ] >We plan to take this up with the authorities, but before we do I would >be very interested to know what it is technically possible for the >phone company to do to trace such calls. I don't really know about the legal side of things, but as a former employee of the UK telephone industry I do know something about the technical side. I'm afraid I have to make the following somewhat cowardly statement about the technical feasability of call tracing: "It all depends". It depends mainly on what kind of switching equipment the call is routed through. In the newer, processor controlled switches, the capability is there to trace the call. Whether it's used or not is another matter, and probably depends as much as anything on what BT feels like doing on a particular day. (I'm referring here specifically to the System X and system Y switches.) On the older equipment (there's still a lot of it around) it becomes more complex. (I'm referring here not only to Strowger exchanges, but also crossbar (TXK1, TXK3) and the old electronic exchanges (TXE2, TXE4)) It is possible to trace calls on these exchanges, but only with considerable effort. It requires engineering personel stationed at the echange where the call is being received. When the offending call arrives, the call can be held, and a path traced back through the switches. This is, of course, tedious and time consuming. Moreover, the call can only be held within the exchange: if the call originated outside the exchange the best you can do is determine which exchange the call came in from, and maybe try and trace through the originating exchange. But if the caller always phoned from a different exchange, this wouldn't do much good. I wonder, however, if there may be a simpler solution for you. BT has a device called a printer meter, which can be attached to a phone line and records dialled digits and meter pulses for that line. Now I wonder if, in the situations you are interested in, that you suspect you know who is causing the harassing calls? Maybe you could arrange to have a printer meter placed on the suspects line. It used to be that since the printer meter only recorded dialled digits and meter pulses, not the actual conversation, no warrant or court order was required to connect it. (An aside: the printer meter was originally designed to help solve billing disputes, but it was found useful by the authorities for detecting all sorts of nefarious activies.) If you have specific questions, I may be able to help; email me. Martin Harriss martin@cellar.bae.bellcore.com