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From: kreed@telesys.cts.com (Kevin W. Reed)
Newsgroups: comp.dcom.modems
Subject: Re: Big problems with modems that aren't grounded. What to do?
Message-ID: <1990Dec4.144946.1243@telesys.cts.com>
Date: 4 Dec 90 14:49:46 GMT
References: <1990Dec4.023427.25652@panix.uucp>
Organization: TeleSys Development Systems, San Diego, CA
Lines: 33

>>>alexis@panix.uucp (Alexis Rosen) writes:
>I posted a query here a month or so ago, complaining about some very strange
>problems with a bunch of 2400bps modems connected to my unix box.
[stuff deleted]
>The problem is that the modems and the computer frequently fail to recognize
>that DCD and/or DTR control lines have been raised. Thus, the modems may not
>answer, and if they do, the getty may not complete the open.

>Is there anything I can do to deal with this situation? If not, I suppose 
>I'll need to get new modems. Which cheap modems have a ground connector? 
>The ones I know of, which are generally trouble free, don't have these.

I've run into this problem several times.  I've seen it caused by two
problems:  1) Not enough power to the modem.  If you have a bunch of
modems plugged into the same strip (outlet) and that circuit is being
overdrawn, the ones with the cheap power supplied (or AC/DC converters)
may not have enough power to operate properly (This sometimes happens when 
you use an adapter from another modem type).
2) Sometimes plugging in a phone into a modem causes it to not work properly
for answering the phone.  The phone rings, but the modem doesn't see it.

I doubt it is caused by a ground problem although I'm not an electrician.

>Thanks,
>---
>Alexis Rosen
>Owner/Sysadmin, PANIX Public Access Unix, NY
>{cmcl2,apple}!panix!alexis

-- 
Kevin W. Reed --- TeleSys Development Systems -- PO 17821, San Diego, CA 92177
TeleSys-II BBS & telesys.UUCP +1 619-483-3890 - Telebit PEP Line +619 483 0965
UUCP: {nosc,ucsd}!crash!telesys!kreed -------- Internet: kreed@telesys.cts.com