From: krisk@Apple.COM (Kris Kreutzman)
Newsgroups: comp.sys.mac.comm
Subject: Re: Apple Talk Remote vs. Noise?
Date: 16 Apr 92 02:37:31 GMT
Article-I.D.: apple.65515
Distribution: comp
Organization: Apple Computer Inc., Cupertino, CA

mjkobb@media-lab.media.mit.edu (Michael J Kobb) writes:

>Greetings!

>  I've recently received my new SupraFaxModem v.32bis, and I've been
>using it to connect with AppleTalk Remote to work.  I'm not using
>ARA so much for Mac-to-Mac connectivity as to get me connected to
>the campus network so that I can open TCP connections to Unix hosts.

>  I'm running into a problem, though.  ARA seems to spontaneously
>disconnect every now and then (frequently enough to make it a royal
>pain to have to reconnect and re-login to the Unix machines).  The
>only message I get is something like, "Your AppleTalk Remote
>connection has been disconnected."  Helpful.

>  I've noticed that the phone line I'm on is a bit noisy.  Indeed,
>after dialing in over a normal serial connection after ARA punted me
>for the third time last night, I was getting quite a bit of line
>noise.  I've also noticed this on voice connections.

>  Question: is ARA susceptible to noise?  I thought it was supposed
>to have built-in error correction.  There are a couple of other
>factors here (the new modem, a custom CCL on the other side), but it
>does work quite well for up to a couple of hours, then just hang up,
>so I'm not convinced that those are the problems.

>  Has anybody had problems with ARA on noisy lines?

>  For you CCL gurus:  if the machine on one end thinks it's
>"CommunicatingAt 2400" while the other thinks it's "CommunicatingAt
>14400", would this cause problems with the error
>correction/detection?  Due to limitations on our hardware at one end
>(no CONNECT message), we've aimed at the lowest common denominator.
>Would this cause my problems?  (No "yeah, probably" messages,
>please.  If you think so, please tell me why.)

>  Boy, I really love the bleeding edge of technology... :-)

>Many thanks!
>--Mike

ARA, like any communications program, can handle line noise.  Up to a point.
However, my suspicion is that it could be your modem and/or script.
Especially after your comments about CCL scripts, if one machine thinks
it is "CommunicatingAt 2400" and the other "14400".  The CommunicatingAt
script command is used to adjust the ARA driver's internal timing.  If the
V.32bis modem is not in "direct mode" and always responds to a connection
with "CONNECT 14400" even when the RAW data rate is actually at a lower speed
then ARA will behave badly.

Now, if you know the speed of the modem you are talking to then you could have
the serial connection to the modem at 19.2k (hardware handshaking is a must),
but set the CommunicatingAt command to the lower data speed, say 2400.  Then
all will be copacetic.
Not a great solution... but SHOULD work...

About being at the "bleeding edge of technology"...
Your not.  Modems are one of the most ancient pieces of technology still
hanging around.  They are cantankerous and you need a P.H.D. in Modomology
to talk their language.  ARA is supposed to sheild the unskilled computer
user from this frightful mess.  But someone still has to write the scripts.
And some modems have problems fitting in the scope of ARA. :-(

Speaking of scripts, here is a question for everyone.
Is there an archive for ARA scripts on the internet?
I MIGHT be able to start one here at Apple... but I can't promise anything...


Kris Kreutzman .... krisk@apple.com
No snappy sig ... Standard disclaimer applies ... 
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