Path: utzoo!telecom-request Date: Sat, 22 Jun 1991 04:35:31 GMT From: Mike Andrews Newsgroups: comp.dcom.telecom Subject: Re: Modem vs. Line-Powered 'In Use' Light Message-ID: Organization: Chinet - Chicago Public Access UNIX 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 478, Message 4 of 9 Lines: 17 In article gsteckel%Ecd@sun.com writes: > Recently I bought a PP 9600-SA modem, and attempted to use it. No joy > -- the best I could do was 4800 BPS. Mysteriously, only the incoming > data were incorrect -- the remote system received my transmissions > essentially perfectly. After a lot of futzing around, I disconnected > a two-line phone with a line powered 'in-use' light. Voila! 9600 BPS > V.32 worked with very low error rates. I'm not a "phone engineer" but I did work as a tech support rep at US Robotics. Your experience was one we watched for. The early Panasonic Easa-phone speaker phones were famous for causing line noise and modem data errors. It's the LED connected directly to the the phone line that does it, as you suspected. I guess it turns into a selective filter that attenuates the modem's signal.