Path: utzoo!telecom-request Date: 6 Jun 91 01:16:49 GMT From: Jim Hickstein Newsgroups: comp.dcom.telecom Subject: Modem Trouble on Subscriber Loop Carrier Message-ID: Organization: Teradyne, Inc. San Jose CA Sender: Telecom@eecs.nwu.edu Approved: Telecom@eecs.nwu.edu X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@eecs.nwu.edu X-Telecom-Digest: Volume 11, Issue 430, Message 10 of 12 Lines: 38 One of my users tried to dial in from home recently, only to discover that the modem spit out garbage continually. He thought it looked like a bad case of a noisy line, but voice calls sounds "crystal clear." I noted that his use of "crystal" indicated that something had gotten better than it was; he said that seemed to be the case. Two such 1200-baud modems showed the same behavior (although one had a history of such problems, and had had its 600-Ohm transformer replaced a while back). Even on calls from one of his residential lines to the other, the same symptoms arise. So this lets out the modem on my end, and the network between his serving office and anywhere else; the two directory numbers have the same exchange, so I suppose they are in the same switch. Thinking fast, I explained that certain adaptive compression and other fancy techniques can cause trouble for modem users. He mentioned that a representative of Pac*Bell had said that they "guarantee service only for voice data [sic]". And the modem worked last week; it just suddenly stopped working. But I thought these techniques were only economical in the long-haul network. Is it possible that the little box on the corner suddenly has a newfangled subscriber loop carrier terminal in it that does some really sophisticated compression, or otherwise makes assumptions about the sort of traffic that will be handled? There has been enormous growth in his neighborhood (he said they had run low on directory numbers, but this doesn't necessarily imply a shortage in the loop plant, I suppose). Are they starting to use something other than straight digitizing on SLCs? Or did both of his modems go south in the same week? Jim Hickstein, Teradyne/Attain, San Jose CA, (408) 434-0822 FAX -0252 jxh@attain.teradyne.com ...!{decwrl!teda,apple}!attain!jxh