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Modems:  Why did I get disconnected unexpectedly?


Q.  I just got disconnected.  I was reading news, had looked away from the
    screen for a moment, and when I looked back (less than a minute), it said
    "NO CARRIER".  What causes this?

A.  There are as many reasons for modem disconnects as there are causes for
    the common cold.  A few of the more popular:

    - Noisy telephone line.  Modems vary greatly in their ability to
      tolerate noise on the line without dropping off.  Second residential
      lines are notoriously noisy -- customers are often given a less-
      desirable pair, or the second line is created using electronic 
      techniques inconsistent with reliable modem use.

    - Call Waiting.  Many people forget to turn this off before every data
      call.

    - Other electrical interference.  Other phones, answering machines, or
      fax machines on the line can cause trouble; unplug them all.  Storms
      or windy days can disturb otherwise quiet and reliable telephone lines.

    - Cheap modems.  The money in making a modem more than basic goes into
      line-conditioning circuitry.  The cheaper the modem, the more it's
      susceptible to all the above; the good and great ones can deal with 
      a surprising variation in line quality.

    - Failing modems.  This is more often on our side than the customers;
      our modems are in 24-hour service, sometimes fail, and are quite
      difficult to identify when they fail only every so often.


Q.  How can I fix this?

    - Unplug everything on the line you're using except the modem.  You'd
      be surprised how often this works.

    - Listen to the line using a good telephone at different times of day
      and week.  See if your line has a pattern of noise at certain times;
      if it does, try convince the phone company of that and have them fix
      it.  This takes guts and time; it took me three years.

    - Make your modem more tolerant of hiccups.  Add the following to your
      modem initialization string in every program that uses your modem:

           S9=16S10=36

    - Upgrade your modem.  Moderately priced, easy-to-set-up, reliable
      modems these days cost around $150-$200.  Always buy external modems,
      so you can watch the status lights to debug line trouble.  We
      recommend the SupraFAX modem because it's simple to set up, reliable,
      reasonably priced, and widely available for both Macs and PC's.  We
      do not recommend the SupraExpress modem for the Mac; although $30 or
      so cheaper than the standard model, it draws power from the ADB port
      (making it more difficult to troubleshoot, as you must turn off the
      computer to turn off the modem) and seems to be generally less
      reliable.

    - Turn off Call Waiting before each call, and make sure no one picks
      up any other extension, preferably by unplugging everything from the
      phone jacks.

    - Report repeated patterns of disconnects to support@halcyon.com.  Real
      Soon Now we'll have a form that'll make this easier; in the meantime,
      include the type of modem, time of day, kind of telephone line you
      have, the number called, length of connect, and what you were doing.
      Don't report individual drops, only patterns.  If you get the same
      behavior many times in a row, wait fifteen minutes and try again.  If
      it still happens the same way, consider that something may have
      changed on your end (unless it's very early in the morning, in which
      case you still might be getting the same defective modem on our end).

    - Hang in there.  Telephone lines were built for voices, not data 
      communications.  That all of this works at these speeds at all is
      somewhat of a miracle.


(09-Apr-96/modwdigd/WRD)
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Copyright 1996  Northwest Nexus Inc.  All Rights Reserved.
This document may not be reproduced nor redistributed in any form without
express permission; contact us at support@halcyon.com with questions.