KFL@AI.AI.MIT.EDU ("Keith F. Lynch") (07/06/88)
> 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. ...Keith
soley@ontenv.UUCP (Norman S. Soley) (07/09/88)
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"
levy@ttrdc.UUCP (Daniel R. Levy) (07/10/88)
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-----|
dave@westmark.UUCP (Dave Levenson) (07/10/88)
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
henry@utzoo.uucp (Henry Spencer) (07/11/88)
The UUUUU... sequence is well-known to be the result of one of the modems erroneously going into test-pattern mode. Modems on time-sharing systems and the like should *always* have remote initiation of test disabled, because otherwise it's easy for line noise to kick the modem into this mode. There is no fix except to break the connection. 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. -- Anyone who buys Wisconsin cheese is| Henry Spencer @ U of Toronto Zoology a traitor to mankind. --Pournelle |uunet!mnetor!utzoo! henry @zoo.toronto.edu
rcdsdgx@dutrun.UUCP (Dik Groot) (07/11/88)
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
bem@homxc.UUCP (B.MCNAIR) (07/11/88)
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
bobmon@iuvax.cs.indiana.edu (RAMontante) (07/12/88)
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..."
thad@cup.portal.com (07/13/88)
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! :-)pbrown@gldsyd.OZ (Peter Brown) (07/15/88)
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.
kuzminsk@thorin.cs.unc.edu (David Kuzminski) (07/16/88)
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 ... ># ># 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-----| Sounds like something is forcing the modems into a test mode. You are not really seeing U's on the screen. What you ARE seeing is a mark/ space test pattern (01010101) that just happens to be the same as an ASCII 'U'. If I remember correctly, the self test pattern is generated by what is called a 'analog loopback test' which tests the analog receiver and transmitter circuitry. This test usually disables the digital interface and the repeating pattern doesn't appear on your screen. There is another test that modems sometimes run called a 'digital' or 'local' loopback which tests the digital part of the unit. The test runs by taking whatever it receives on the TX line and turning it around and back out the RX line. It sound like this test may be running when you the modem is echoing locally. There are special codes that one can send a modem to put it into test modes remotely. It sounds like perhaps these units are recieving what they believe to be these codes.