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000411_news@newsmaster….columbia.edu _Fri Sep 26 11:25:03 1997.msg
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From: fdc@watsun.cc.columbia.edu (Frank da Cruz)
Newsgroups: comp.protocols.kermit.misc,comp.dcom.modems,comp.std.internat
Subject: Re: Kermit as a terminal for V.18-capable modems
Date: 26 Sep 1997 15:24:56 GMT
Organization: Columbia University
Lines: 107
Message-ID: <60gk48$6se$1@apakabar.cc.columbia.edu>
References: <609at2$jf1@gateway.dircsa.org.au>
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Xref: news.columbia.edu comp.protocols.kermit.misc:7736 comp.dcom.modems:200726 comp.std.internat:7178
In article <609at2$jf1@gateway.dircsa.org.au>,
Arthur Marsh <arthur@gateway.dircsa.org.au> wrote:
: Over the last few years work has been going on to develop an ITU-T
: Recommendation for a modem that would inter-work with text telephone devices
: currently in use around the world.
:
: One can find out about this work at: http://www.pi.se/~omnitor, particularly:
:
: Linkname: V.18 final version __DETERMINED__( Q09a10r2.doc )
: URL: http://www.pi.se/~omnitor/q09a10r2.doc
:
: for the current version of ITU-T Recommendation V.18.
:
: In it, ISO 10646 is used as the character set.
:
: This is interesting as I have not previously seen any modem explicitly
: supporting double byte character sets, and wonder how an external
: V.18-compliant modem would do so, and what non-propriatary-to-the-V.18
: -compliant modem terminal software e.g. Kermit-95 would do to handle double
: byte character sets, given that modems currently use 8 data bits 1 stop bits
: no parity for commands and responses.
:
: Is there a standard sequence in ISO 10646 that can be used to tell a terminal
: package to enter ISO 10646 mode? Presumably the V.18-compliant modem could
: also accept and send data as single-byte Latin-1 characters.
:
I'm looking at one of the V.18 documents now. Like all ITU-T (formerly
CCITT) docments, it requires more than a casual browsing. A couple quick
reactions (pardon me if I'm missing something very basic -- I can't use the
Microsoft Word document):
1. ITU modem command-language standards have never caught on. What about
V.25bis, which is at present the ONLY international standard in this
area? As far as I know, it is used in Brazil (by law) and nowhwere
else. This is yet another area that is driven by the chaotic
marketplace, where the de facto "standard" is the Hayes AT command set.
But of course, this varies wildly in both syntax and semantics from one
modem to the next. Nevertheless, we can see that most makers of
communication software (other than the Kermit Project) feel it is quite
safe to ignore all non-Hayes modem command languages, even the
international standard one, the paramount example of this being
Microsoft TAPI.
2. I don't think ISO 10646 is an issue; only regular, unaccented Roman
letters are used in text-telephone messages. Quoting:
The initial condition of the converter shall be the Letters (LTRS) mode,
therefore the DCE shall send the LTRS character (11111) to the line prior to
transmitting the first translated character. The receiver decoding shall also
start up in the LTRS mode. Additionally, the DCE shall send the appropriate
mode character (i.e., LTRS or FIGS) every 72 characters.
The 5-bit codes supported are given in Tables A-1 and A-2. Each character
shall consist of the 5-bit sequence given in the tables preceded by a one
start bit and followed by a minimum of one and one half stop bits.
The DCE shall convert the 5-bit coded characters received from the line to the
appropriate 7-bit coded characters and transfer them to the DTE on circuit 104
(or its equivalent).
The DCE shall convert the 7-bit coded characters received from the DTE on
Circuit 103 (or its equivalent) to the appropriate 5-bit coded characters (see
Annex A) and transmit to the line.
(End quote)
Please correct me if I am wrong.
Appendix 2 says something about ISO 10646, but I can't find any reference
to Appendix 2 anywhere else in the document
: This is interesting as I have not previously seen any modem explicitly
: supporting double byte character sets, and wonder how an external
: V.18-compliant modem would do so...
:
Appendix 2 says that the default character set (for what?) is Level 1,
2-byte ISO 10646 sent as two conventionally framed 8-bit bytes.
: ... and what non-propriatary-to-the-V.18
: -compliant modem terminal software e.g. Kermit-95 would do to handle double
: byte character sets, given that modems currently use 8 data bits 1 stop bits
: no parity for commands and responses.
:
According to V.18, that will not change. UARTs are UARTs, etc. To send a
2-byte character, one sends two one-byte characters.
Kermit 95 will support double-byte character sets in a future release.
: Is there a standard sequence in ISO 10646 that can be used to tell a terminal
: package to enter ISO 10646 mode? Presumably the V.18-compliant modem could
: also accept and send data as single-byte Latin-1 characters.
:
Yes, the standard for character-set designation and invocation
is ISO 2022. Character sets are registered by the ISO in the International
Register of Coded Character Sets to be Used with Escape Sequences, which is
maintained on behalf of the ISO by the ECMA.
By the way, transmission of bare Level-1 ISO 10646 (which is equivalent
to "bare" Unicode) is problematic in general, and in most arenas where
Unicode is used internally, a different transfer format, such as UTF8, is
used that is compatible with ASCII and Latin-1. In some cases, as in the
Plan 9 Operating System, UTF-8 is used internally as well.
Clearly there will be a lot of "shaking out" in this area in the coming
years.
- Frank