Are you experiencing strange line-noise problems with your modem sometimes, but not all the time? I'd like to share a recent experience and perhaps spare some of you the full agony of troubleshooting such a problem.
One of my fellow user-group members and a user of my bulletin board, Memory Alpha, had been complaining that he could call CompuServe when his PowerBook's PowerPort/Gold modem was hooked to his upstairs phone jack, but when he plugged the PowerPort/Gold into his downstairs phone jack, his connections always failed; the screen quickly filled with garbage. Neither Global Village (the PowerPort's manufacturer) nor I could come up with any reason that he should reliably see such different results using two different jacks on the same phone line.
After I offered a few suggestions via email, none of which helped, I decided to visit and try to analyze the problem directly. Naturally, when we sat down so he could demonstrate the problem at his downstairs phone jack, we connected to CompuServe just fine.
Figuring that this was an intermittent problem (despite his insistence to the contrary), I fiddled a bit, and showed him how to activate the modem's error correction from within CompuServe's Navigator software. This, I felt, should help even if the problem returned. (Ithaca is lucky enough to have a local CompuServe access number equipped with a high-speed modem and error correction.) Not wanting to give up without seeing the problem at all, we tried from the upstairs jack. Worked fine. We then returned downstairs... and suddenly saw exactly the problem he'd been describing!
What had changed? We realized that, after our brief experiment upstairs, we'd left the telephone plugged in. Some further experimentation proved that, as long as that phone wasn't plugged in, the modem worked fine either upstairs or downstairs. With the phone plugged in, though, we were reliably unable to get a connection from the downstairs jack.
The moral of this story? Well, despite all reason, it seems that sometimes other devices on the line interfere with your modem connection, even when the devices are on-hook and seemingly inactive. Most likely the problem is due to the fact that this is an electronic phone, which draws a little bit of power from the line even when it's not "doing" anything. Before tossing your modem in the junk-heap or angrily exchanging it for another brand, you'll want to check your wiring and try temporarily removing phones or other devices from the line.