SUMMARY: modem won't answer

From: Gary Casterline (
Date: Thu May 16 1991 - 14:03:30 CDT

My original plea:

>From: Gary Casterline <>
>Subject: modem won't answer
>Date: Wed, 15 May 91 23:37:41 PDT
>Oh experienced ones,
>This is my first time introducing a Sun to a modem. I can call out ok,
>but when I call in the modem won't pick up. However, if I tip directly
>into the modem, and then call in using the phone on my desk, the modem
>answers on first ring and puts out a healthy squeal.
>Modem: zoom 42.bis (I've set S0=1, which is supposed to set it
> answer after one ring.)
>Sun: sun4/470 SunOS-4.1.1, ALM2
>`ls -l /dev/ttyd?`:
>crw--w--w- 1 root wheel 44, 0 May 15 15:40 /dev/ttyd0
>crw--w--w- 1 root wheel 44, 1 May 10 06:29 /dev/ttyd1
>`ls -l /dev/cua?`:
>crw------- 1 uucp wheel 44, 128 May 15 23:18 /dev/cua0
>crw------- 1 uucp wheel 44, 129 May 15 22:28 /dev/cua1
>`grep ttyd /etc/ttytab`
>ttyd0 "/usr/etc/getty D2400" dialup remote on # 642-1767
>ttyd1 "/usr/etc/getty D2400" dialup remote on # 642-1768
>Gary Casterline Agricultural & Resource Economics
> 207 Giannini Hall
>(415) 642-5583 UC Berkeley, CA 94703

I got lots help from those listed below. I looked them over
and decided to try the easiest one first:

From: etnibsd!vsh@uunet.UU.NET (Steve Harris)
        I may be wrong, but...

        The only thing missing from your report was the output of:

                ps ax | grep getty

        to see if there is a getty on ttyd0. This is just a guess, but
        I suspect there is not, and that consequently the Sun is not
        asserting DTR, so the modem won't answer.

        If this hypothesis is correct, the problem is in the ttytab
        file. Try removing the word "remote" -- I think Sun's init
        does not know what to do with it.

        As I understand it, a port is either "on" or "off", other
        options are "secure" (allow root logins) and "local"
        (ignore/simulate DCD).

        Please summarize.

        Steve Harris - Eaton Corp. - Beverly, MA - uunet!etnibsd!vsh

I did this, and the modem now answers on first ring. Thanks!
Here is a breif summary of the other hints I would have tried next:

From: Claus Assmann <>

        It has to be initialised with a string ("ATZ")
        Up to now, I start the modem every night (it's only
        used twice a night, and the other time I need the phone !)
        manually with
        % tip cua0

From: (Richard Pyle)

        Most modems can be configured so that they will not answer
        unless DTR (pin 20) is high. Sun does not assert DTR high until
        the port is active (as it becomes with tip). if the sun is
        equiped with CD set to hardware control then getty will attach
        on the rise of CD from the modem. The solution is (I think) to
        look through the documentation of the modem to be sure that DTR
        is not controling its answer. (i.e. DTR ignored for answer)

        rich pyle

From: griger@isis.cgd.ucar.EDU (JoAnne Griger)

        this is so silly, what i'm about to say, but i've installed
        many modems on suns, and like many people, overlook the most
        obvious and simple solutions. i've experienced the same
        problem you described.

        as long as the software is set up correctly, the hardware
        should be installed *after* the software is (this actually is
        written somewhere but i can't remember where). so, maybe all
        you have to do is power cycle the modem...

        hope your solution is this simple...

        JoAnne Griger (
        National Center for Atmospheric Research
        303 497 1376

From: (Geert Jan de Groot)

        A modem usually doesn't pick up if the DTR line isn't true. It
        also kicks you off if DTR runs false. There is a similar
        mechanism with DCD: this signal, fed by the modem, will log you
        out when the modem loses carrier.

        Connecting a modem is DIFFICULT if you do it for the first
        time. I would suggest contacting someone of another department
        of berkely that helps you. If you need help by me, just ask,
        but include SUN PROM version number, the config file of the
        kernel, and the exact layout of the cable you're using, and the
        output of the eeprom command.

        If you got things right, the modem should fall off if you log
        out, and if you pull the plug of the telephone wire, the modem
        should cause you to log out automatically.

        Geert Jan


From: Mike Raffety <oconnor!>

        You have to tell the modem to answer the phone regardless of
        whether DTR is high ... see your modem manual ...

From: stern@sunne.East.Sun.COM (Hal Stern - Consultant)

        is the modem expecting a signal on DTR? it may not be wired to
        get one. also, what is the modem doing with DCD? the fact
        that it picks up when you tip into it hints that it may want
        DTR but may not see it all of the time


From: truth! (Peter Gutmann)

        There are two things to look at.

        1) Modem configuration.

        The modem needs to be configured to have the carrier detect
        follow the DTR on the modem. The sun getty uses the carrier
        detect to trigger the login sequence.

        2) DTR

        using the software carrier detect (ttysoftchar(1) on the sun4
        machines or reconfiguring the kernel on sun 3's) is the key.
        Most modems will not answer the phone with out the DTR signal
        being present.

        Hope this helps

        Peter Gutmann

Thanks again to you all.

Gary Casterline Agricultural & Resource Economics 207 Giannini Hall
(415) 642-5583 UC Berkeley, CA 94703

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