From: gerg@netcom.com (Greg Andrews)
Subject: Question on TIES (was Re: Question on Hayes ad)
Date: Mon, 28 Sep 92 07:20:35 GMT
Organization: Netcom Online Communications Services (408-241-9760 login: guest)
Distribution: world               

In article <dkw02685920825123551@wolferts.ka.sub.org> dkw@wolferts.ka.sub.org (Klaus Wolferts) writes:
>wolfgang@netcom.com (Wolfgang Henke) writes:
>>
>> This is an argument against TIES and the Hayes patented escape sequence.
>> Turning off in-band escapes with S2>127 should alleviate the problem.
>
>There are two several problems to be looked at:
>
>Is there any exact definition of the TIES mechanism? 
>

I've seen a document from the creator, which was placed in the public
domain.  The document specifies a good number of things, but it does not
specify EVERYTHING.  If it did, TIES probably wouldn't be used by other
modem manufacturers.  There needs to be some room in such a specification
to let different implementors handle the unique needs of their own modems.
The creator of TIES isn't arrogant enough to think they know everything
there is to know about all the different brands of modems, so they left
some of the minor details undefined.

>
>If only the sequence <3 escape chars> <valid modem command> is valid
>then there will come up two problems:
>
>1) nearly every modem uses a different command set or at least 
>different extensions to the "hayes standard" as fas as there is 
>existing any (is there any?? :-) 
>

I think there is.  There is, at the very least, the command "AT"
followed by a Carriage Return.  That is a valid "Hayes compatible"
command, which causes the modem to say "OK".

>
>2) lots of commands end with parameters (i.e. ATSn=xxx where n and 
>xxx vary with n from model to model and xxx with n and model).
>The decision whether a specific command is valid or not eventually 
>needs a complete command parsing which could include up to 40 chars 
>(the standard?? command buffer length) for several commands in 1 line. 
>
>So where is the decision final? After the first AT or A/ ? It 
>depends on the designers decision which no one knows as far as 
>there is no standard and therefore probability calculations are of
>theoretical nature only.
>

No, the calculations assume the command is the one I described above.
"+++" followed by "AT", followed by a Carriage Return.  A six character
sequence, that will cause a TIES modem to escape to command mode and
stay there.  I don't recall for sure, but the TIES description may
actually specify AT^M as a VALID command, so software can reliably
control different brands of modems.

The decision about what commands are valid is left to the modem makers,
so they can adjust the escape sequence to meet the needs of their own
modems.

>
>But there is another problem, (bug or feature :-) which upsets me 
>much more (and I brought it up once before but the discussion moved 
>to other points of interest): 
>
>   when an escape sequence (be it Hayes or TIES) is recognized, why 
>   is it tranferred to the line and not eaten by most modems ?????
>
>   A recognized escape sequence has nothing to do on the line, 
>   its for the modem only (and will honoured by it anyway!!)
>

You're forgetting that the modem can't recognize the sequence until
after all three plus signs have been sent.  In the Hayes style sequence,
the modem can't recognize the sequence until after a PAUSE that comes
after the sequence!  Before the modem has detected the full sequence,
it must pass the characters through to the other modem.  Witholding
characters is not what you, the purchaser of the modem, want it to do!

(Imagine a modem that doesn't pass the "+" escape character.  Now imagine
how the modem will behave transferring a file with lots of "+" characters
in it.  It will transfer slower than a file with different data!)


>
>What would you tell your printer (or other devices) manufacturer or 
>dealer, if it would not only recognize the escape sequences for 
>controlling the printer features but also print them on the paper 
>output ??? 
>

This is comparing apples to oranges.  Printer escape sequences start
with a character that is not printable in the printer's normal character
set.  The same is true for terminals such as the VT-100.  That is using
an OUT OF BAND escape rather than an IN BAND escape.  



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