TM> Been speaking to Telstra service and difficulties for the last
TM> few days. Although quite helpful, we still haven't been able to
TM> track this problem down. It's a doozy.

TM> What is happening is that modem speeds up to 14.4k work fine, but
TM> going the next step to 28.8k is no good. I get good reliable
TM> 28.8k connects (V42/LAPM) but then there are pauses of varying
TM> lengths between screen displays from the remote modem. The pauses
TM> get worse and worse and usually, within 2 or so minutes it hangs
TM> up, "click". NO CARRIER.

We know.  Same here.  My 711/809 line is just about totally unusable as a
BBS during the day.  (It seems to be worse during peak times - with
absolute misery setting in early afternoon and remaining until early
evening.)

The only consolation is that my fax line was worse.  I had it disconnected,
after a job that I needed couldn't connect for a week straight, and went
away.

TM> For some strange reason, I can go much longer without losing
TM> carrier if I am logged into my Internet Service Provider with PPP
TM> and Winsock as opposed to connecting to a bulletin board using
TM> say, Telix.

This is software setup tolerance in action.  The Winsock is actually
loosing carrier, and refusing to hang up. Eventually the modems resync, for
the better cases.  It's possible that setting a ghastly long carrier
dropout time on both ends will make the modems capable of riding through
the junk.

TM> Turning off the modem's error correction so that I can see what
TM> is happening on the line shows me random, short bursts of what
TM> "looks" like line noise.

I've actually caught it.  It's a set of impulses, about 1 per second,
running at just enough level to make my S/N ratio 16db vis the pleasant 36
or more that the lines give when the bastard isn't there.  

Plainly audible - if the modems both shut down.  It may well be triggered
by the modems - I've tried monitoring a silent line for several hours
during the trouble peak time, and never heard it.

It's also been seen to affect one direction only at a time.  (Could be
statistical, in which case it could hit both if you're unlucky.  Unknown.)

When in full cry, the modems can't hold even at 4800baud on that direction,
even though 31200 is still locked fine the other way.

TM> The thing is that these lines have never suffered from line noise
TM> before and there is no trace of it at slower speeds than 28.8k.

TM> Enquiring further this morning, a Telstra chap has now told me I
TM> am on a "BAR 66- digital AXE" exchange. I'm in the Tullamarine
TM> 9335-xxxx area. According to him, this type of exchange is quite
TM> new - perhaps that is the problem, as for a short period last
TM> year I was able to use 28.8k on this line quite successfully.

TM> Has anybody else experienced or heard of this sort of problem
TM> before? I'd really like to sort this one out as using just 14.4k
TM> on my new V34 modem is a real bummer.

14.4 won't help all that much.  When this really gets going, 9600 is a wish
dream as well.

TM> This reminds me. The problem is definately not computer hardware
TM> related, I've tried 3 different computers, 3 different modems
TM> (SimpleModem, Hayes and Motorola) and swapped and changed every
TM> possible cable and power supply. It's definately something with
TM> the line and/or exchange.

Ditto.  Microcom VFAST, Hayes V34 Optima 288, and USR Courier V.Everything.
Exactly the same gross symptoms, same failure rate.

The Courier gives beautiful diagnostic logs, and is building me up a
statistical base.   I offered logs to Frank Nitzche, and he hasn't taken me
up on it yet.  IMHO, he knows, well and truly, with far better logs and
details than we have.

TM> ps. Before anybody asks (Telstra did). No, I don't have an old
TM> T200 phone connected to this line :-)

  Who, us ask that?  :-)  (No I don't have one either.  Modems
direct connected to the lines, no handset at all. :-)

Regards,
Dave Hatch.

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