Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!asuvax!hrc!godzilla!dalyb From: dalyb@godzilla.UUCP (Brian Daly) Newsgroups: sci.electronics Subject: Re: Trace-Back on phones Summary: References for Signalling System #7 (trace back on phones) Message-ID: <47d202ed.1423f@godzilla.UUCP> Date: 3 Jan 90 21:28:58 GMT References: <6693@lindy.Stanford.EDU> Distribution: sci Organization: gte Lines: 48 In article <6693@lindy.Stanford.EDU>, sorka@ucscb.UCSC.EDU (Alan Waterman) writes: > > In article <4344@aplcen.apl.jhu.edu> jdc@aplvax.jhuapl.edu (James David Cover) writes: > >The question I have is whether or not anyone knows anything about whether or > >not one can run a traceback on a phonecall. A friend of mine says that the > >phone company is now transmitting a "header" with the call that, if one knows > >the format, could decode it at display the calling number. > > > >I would appreciate any information, possible ic's that might do the decoding, > >theory, specifications, etc. Please reply via e-mail. Thanx. > > > > J. David Cover (jdc@aplvax.jhuapl.edu) > > > I would also like to get info on this subject. An answer to your question is yes -- you can run a traceback on a phonecall provided your system is using signalling system #7 and you have the feature for customer originated trace available. The displaying of the calling number is performed with the use of CCITT Signalling System #7. This provides centralized message exchange on common data channels operating at a transmission rate of 64 Kbps. The system can be divided into two parts: the message transfer part (MTP) and the user part (UP). The MTP contains all the requirements necessary to ensure reliable transmission of messages. The User Part is used for a particular service; i.e. telephony. Signalling system #7 is just starting to emerge into the United States telephone network; there is more than upgrading of a central office that needs to be included into the network (for example, there are signalling transfer points that must be installed). Not all areas have started using SS7. There are many features available with the use of SS7; calling number display, automatic callback, customer originated trace are just a sample. These services are provided by the operating company for a subscription fee. The has been many articles in the telephony literature over the past several years describing signalling system #7. Telephony magazine from February 9,1981 has a good introductory article. I also believe IEEE Communications magazine has had articles devoted to SS7, but I don't recall which issue. Research into signalling system #7 will answer your questions. Brian K. Daly AG Communication Systems, Phoenix, Arizona PO Box 52179, Phoenix, Arizona 85072-2179 Phone: (602) 582-7644 The above comments are my own and do not in any way represent AG Communication Systems.