🚀 go-pugleaf

In article <407880.880706.KFL@AI.AI.MIT.EDU>, KFL@AI.AI.MIT.EDU ("Keith F. Lynch") writes:
> My Hayes 1200 gets into this mode once every few dozen hours of use.
> It doesn't seem to correlate with what I'm doing.  It sends a bunch
> of UUUUU to the host, and locally echos anything I type.  I can't
> find a way out of it except to turn it off and on again.
> 								...Keith

I've experienced this myself and the cause was, get this, ringing tone
on the line. The only way this can happen is if the phone company has
got your line crossed with someone elses, they recieve a call and you
get ringing voltage on your line. This also shows up as billing for
long distance calls you didn't make and so on. 

-- 
Norman Soley - Data Communications Analyst - Ontario Ministry of the Environment
UUCP:	utgpu!ontmoh!------------\              VOICE:	+1 416 323 2623
	{attcan,utzoo}!lsuc!ncrcan!ontenv!norm	ENVOY:	N.SOLEY
    "ZIK ZAK -- We make everything you need and you need everything we make"

In article <407880.880706.KFL@AI.AI.MIT.EDU>, KFL@AI.AI.MIT.EDU ("Keith F. Lynch") writes:
# > From: "Benjamin I. Goldfarb" <goldfarb%hcx9%ucf.CSNET@RELAY.CS.NET>
# 
# > OH YEAH?  More likely the "UUUUUUUUUUU" was an erroneously
# > initiated test mode in the modem in question.  Racal-Vadics are
# > notorious for this ...
# 
# My Hayes 1200 gets into this mode once every few dozen hours of use.
# It doesn't seem to correlate with what I'm doing.  It sends a bunch
# of UUUUU to the host, and locally echos anything I type.  I can't
# find a way out of it except to turn it off and on again.

I've also had this happen with my (Hayes-commandalike) Anchor Automation
Volksmodem 12.  Similar to the Hayes described above, I see UUUUU... on the
screen and then it begins to locally echo.  Weird.
-- 
|------------Dan Levy------------|  THE OPINIONS EXPRESSED HEREIN ARE MINE ONLY
|    AT&T  Data Systems Group    |  AND ARE NOT TO BE IMPUTED TO AT&T.
|        Skokie, Illinois        | 
|-----Path:  att!ttbcad!levy-----|

In article <2799@ttrdc.UUCP>, levy@ttrdc.UUCP (Daniel R. Levy) writes:
> In article <407880.880706.KFL@AI.AI.MIT.EDU>, KFL@AI.AI.MIT.EDU ("Keith F. Lynch") writes:
> # > From: "Benjamin I. Goldfarb" <goldfarb%hcx9%ucf.CSNET@RELAY.CS.NET>
> # 
> # > OH YEAH?  More likely the "UUUUUUUUUUU" was an erroneously
> # > initiated test mode in the modem in question.  Racal-Vadics are
> # > notorious for this ...

The standard data-transfer mode for an AT&T 212-compatible 1200 bps
full-duplex modem calls for scrambling (by the sending modem) and
unscrambling (by the receiving modem) to prevent long strings of
identical bits from being sent over the communication line.  The
scrambler exclusive-or's the data bit-stream with UUUUU (actually,
alternating 1 and 0 bits).  This is helpful in that during idle time
(between characters, for example) the modems get to re-synchronize
by identifying the 0 to 1 or the 1 to 0 transitions.  If you send a
_very_long_ string of UUUUU or ***** in your data, you may defeat
the purpose of the scrambling circuits, and cause the modems to lose
sync with each other.  The result could then be that during
subsequent idle time, you will see the behaviour you've described.

The other possibility is that you've gotten the modem into self-test
mode.

-- 
Dave Levenson
Westmark, Inc.		The Man in the Mooney
Warren, NJ USA
{rutgers | att}!westmark!dave

In article <407880.880706.KFL@AI.AI.MIT.EDU>, KFL@AI.AI.MIT.EDU ("Keith F. Lynch") writes:
> My Hayes 1200 gets into this mode once every few dozen hours of use.
> It doesn't seem to correlate with what I'm doing.  It sends a bunch
> of UUUUU to the host, and locally echos anything I type.  I can't
> find a way out of it except to turn it off and on again.
> 								...Keith

The ASCII representation of ..UUUUU.. (with 8 databits, no parity, 1
stopbit) exactly matches a 1200HZ square wave. Could there be something
in the various modems, that is oscillating freely (at the correct
baudrate) ?
                                            Dik Groot .
-- 
{ - - - - - - - - - - - - - - - - - - - disclaimer : I usually lie. }
Dik Groot,   Delft University of Technology,   Rekencentrum,   DUneT.
Postbox 354, 2600 AJ Delft.  ptt: (31)-15-781938  fax: (31)-15-786522
BITNET/EARN: RCDSDGX AT HDETUD1          usenet/eunet: rcdsdgx@dutrun

In article <239@westmark.UUCP>, dave@westmark.UUCP (Dave Levenson) writes:
> In article <2799@ttrdc.UUCP>, levy@ttrdc.UUCP (Daniel R. Levy) writes:
> > In article <407880.880706.KFL@AI.AI.MIT.EDU>, KFL@AI.AI.MIT.EDU ("Keith F. Lynch") writes:
> > # > From: "Benjamin I. Goldfarb" <goldfarb%hcx9%ucf.CSNET@RELAY.CS.NET>
> > # 
> > # > OH YEAH?  More likely the "UUUUUUUUUUU" was an erroneously
> > # > initiated test mode in the modem in question.  Racal-Vadics are
> > # > notorious for this ...
> 
> The standard data-transfer mode for an AT&T 212-compatible 1200 bps
> full-duplex modem calls for scrambling (by the sending modem) and
> unscrambling (by the receiving modem) to prevent long strings of
> identical bits from being sent over the communication line.  The
The 212 scrambler is a linear feedback shift register designed to prevent
long runs of 1s or 0s on the channel and the attendant signal power density
problems on the telephone channel and modem synchronization problems.  One
of the test modes of the modem is remote digital loopback, where the remote
modem loops back its output and retransmits the signal for end-to-end
testing.  The way you put the remote modem into digital loopback is by
sending it a constant string (of 0 or 1, I forget) ON THE CHANNEL -
something that a self respecting scrambler would generate infrequently on
its own.  Thus, a modem could be fooled into thinking that it had been
asked to go into remote digital loopback if it heard a constant string of
channel symbols.  The symptoms of false remote digital loopback would be a
10101010 sequence emitted from the modem - which looks like UUUUUU.  This
falsing could occur (1) if the input to the sending modem happened to
scramble as a constant output or (2) if channel conditions caused a
constant string to be detected.

Bruce McNair
AT&T Bell Labs
Holmdel, NJ

henry@utzoo.uucp (Henry Spencer) writes:
>
>The 2400-baud equivalent of UUUUU is wwwww.  The former is known as "the
>marching umber hulks"; I haven't heard an equivalent name for the latter.


"The gushing water lords", surely.  I just ordered my very own opportunity
to experience this...


>Anyone who buys Wisconsin cheese is|  Henry Spencer @ U of Toronto Zoology
>a traitor to mankind.  --Pournelle |uunet!mnetor!utzoo! henry @zoo.toronto.edu

-- makes me wanna go get some good Wisconsin cheese; it's either that or die.
-- 
--	bob,mon				(bobmon@iuvax.cs.indiana.edu)
--	"In this position, the skier is flying in a complete stall..."

As a user of hundreds of different modems (which I've had to test for use
with my products), the "UUUUU..." problem is a symptom of having been
forced into { analog | digital } loopback test and/or another test routine(s).

if you glance at your ASCII chart, receipt of "UUUUU..." is the bit-stream:

    0101010101010101010101010101.....

Most "reasonable" modems have either a DIP-switch and/or a soft-option to
disable any and all remote and local digital and analog (loopback) tests;
I disable ALL that junk if possible, and if the modem doesn't support
disabling those options, then I toss the modem out the window and over the
fence (there are a LOT of modems out there now, and the fence collapsed last
year! :-)

In article <2799@ttrdc.UUCP> levy@ttrdc.UUCP (Daniel R. Levy) writes:
>In article <407880.880706.KFL@AI.AI.MIT.EDU>, KFL@AI.AI.MIT.EDU ("Keith F. Lynch") writes:
># > From: "Benjamin I. Goldfarb" <goldfarb%hcx9%ucf.CSNET@RELAY.CS.NET>
># 
># > OH YEAH?  More likely the "UUUUUUUUUUU" was an erroneously
># 
># It sends a bunch
># of UUUUU to the host, and locally echos anything I type.
>
>Similar to the Hayes described above, I see UUUUU... on the
>screen and then it begins to locally echo.  Weird.
>-- 

I have an Australian made Data Bridge modem that exhibits the same symptoms
when I turn it off after use. I leave it on all the time now.