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From: lstowell@pyrnova.pyramid.com (Lon Stowell)
Newsgroups: comp.sys.hp,comp.dcom.modems
Subject: Re: HP37212B modem refuses to answer phone!!!
Keywords: no answer on incoming calls
Message-ID: <153266@pyramid.pyramid.com>
Date: 26 Apr 91 00:55:46 GMT
Sender: daemon@pyramid.pyramid.com
Reply-To: lstowell@pyrnova.pyramid.com (Lon Stowell)
Organization: Pyramid Technology Corp., Mountain View, CA
Lines: 40

In article <1991Apr25.154031.2013@cv.ruu.nl> bartm@cv.ruu.nl (Bart Muyzer) writes:
>Hi,
>
>I'm experiencing a problem with a HP37212B "Error Correcting Modem". I know
>what causes it but I don't know what to do about it (except rebooting :-( ).
>The modem is connected to a HP 9000/835 using a mux which (among others) also
>attaches the system console to the system. This one works fine so I know it's
>not the mux.
>
>The problem is that the modem refuses to pick up the phone because the MDTR
>is low. So it thinks the connected computer isn't ready and refuses to
>answer. This situation occurs after the following sequence:
    
    The problem is NOT the modem, it is the [ software in ] the
    computer.   As you note if DTR is low, the modem passes RI
    to the computer....(which is obviously ignoring it...).

    When you change the modem to set DTR high, the modem
    answers...  [so the modem is performing perfectly normal]
    but you get no login....[which means the computer is dead]


>* user calls and logs in
>* user initiates to be called back
>* user hangs up and gets called back
>* user works and hangs up
   At some point after this, the computer [ software ] should be
   raising DTR to take another inbound call.   This actually
   looks like a system problem...in that magically one user gets
   in, gets called back, and can access the computer.

   Something is drastically wrong with the exit routine which is
   leaving the port inoperative.   Either the port should again
   raise DTR (so the modem can answer automatically) or it
   should detect RI, then raise DTR so the modem will answer.

   You don't have a modem problem, you have a software problem.
   Either that or your MUX is messing with the DTR signal from
   your computer.   If you have a breakout, see if the computer
   has DTR on ( or will raise DTR if RI is high ).