Re: GSM 03.38 substitution character?

[Markus Scherer <markus.icu@gmail.com>]

On 11/2/06, Frank Ellermann <nobody@xyzzy.claranet.de> wrote:
> http://www.3gpp.org/ftp/Specs/archive/03_series/03.38/0338-720.zip
> I can't really read it, it's a *.doc, but it might be what you want.

Thanks, this is great!

I can't find any reference to a substitution character (searching for
"subs" and "repl" and reading portions of the text). I guess the
intention is for a sender to switch to UCS-2 if the text can't be
represented in the "default alphabet". In which case any value should
do for a conversion table because the conversion should really stop on
unmappable characters. If anyone can find something that I am not
seeing, please let me know.

There are a couple of places where the unicode.org table seems to
differ from this text (0338-720.doc): (In addition to the ç mentioned
in the unicode.org table.)

1. A 0x1B alone should be a space (one-way to-Unicode) but the Unicode
GSM table has it round-trip to U+00A0 NBSP. (The text says "This code
is an escape to an extension of the 7 bit default alphabet table. A
receiving entity which does not understand the meaning of this escape
mechanism shall display it as a space character.")

2. The pair 0x1B+0x1B should also map to a space (one-way to-Unicode)
but the Unicode GSM table does not include this combination. (The text
says "This code value is reserved for the extension to another
extension table. On receipt of this code, a receiving entity shall
display a space until another extension table is defined.")

Thanks,
markus