irssi/docs/help/in/recode.in

@SYNTAX:recode@

RECODE
    %|List the conversion database

RECODE ADD %|[<target>] <charset>
    %|Add an entry to the conversion database (if target is omitted,
    the current channel or query will be used)

RECODE REMOVE %|[<target>]
    %|Remove an entry from the conversion database (if target is
    omitted, the current channel or query will be used)

To specify your local charset you have to set term_charset

Example:

/SET term_charset <charset>

To see the recode settings: /SET recode

You can change them with /SET 

Examples:

/SET recode_fallback <charset> 
to set the fallback charset for incoming events

This charset is used if your term_charset is UTF-8
and the conversion for the target is not set and
the text is not UTF-8.

/SET recode_out_default_charset <charset> 
to set the global outgoing charset

When it's set to a charset it will be used
if no conversion for the target is set.

/SET recode_transliterate ON 
to enable the global transliteration.

The transliteration is based on your locale settings, 
if it doesn't work properly your locale settings may be wrong.
You can enable it per target by adding //TRANSLIT to the <charset>

Hint: <charset> can be almost everything listed by 'iconv -l'