ludo@amdahl.UUCP (04/09/87)
We observed a strange phenomenum with our u.s. robotcis courier 2400 modems.
We have some people dial in from home (short distance, but different phone
switches) with such a modem at both ends. We use the table top model on both
ends.
What we get is medium to large quantities of unrecognizable data in the middle
of a session, usually containing stuff that looks like xoff (DC3). after hitting
CTRL Q a couple of times, we can usually get it going again. At the same time
we observed 2 more phenomena :
The HS led will alternate off/on at a frequency of about 1/second for a dozen
or so seconds on the remote modem, and then stabilize to HS (what we use).
Also at at least one occasion the local modem goes to low speed while the
remote modem stays at HS. Data going from the host to the line will make the
SD led light up, but the remote modem does not have RD lighting. Same thing
at the remote end.
We heavily suspect the modems, which are at software level 243, but do not
know for sure it is the modems and not the phone company. By elimination we
excluded our host and terminals already, but would like to know if anybody
in netland observed similar behavior.
The other locally connected lines are at higher speeds with null modems, so
almost no testing was done with the local and remote modem on the same switch.
When using a Fujitsu V22bis modem and a courier modem for a similar connection
the same thing happens, but a lot lessfrequent. Also the Fujitsu modem has a
less attenuated carrier than the courier. When dialing over real bad phone
connections, it will connect while the robotics will definately not connect.
We also noticed the us robotics modems get extremely hot (have not been powered
off for at least a year), and are wondering whether they just fry themselves
--
Ludo J. M. Vennekens
(408) 737-5074
...{seismo,hplabs,ihnp4,sun}!amdahl!ludo
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