On 2016-04-13 12:47:56 +0000, Wolfgang Schuster said:

> Nicola 13. April 2016 um 14:17 
> On 2016-04-13 11:53:51 +0000, Hans Hagen said: 
> 
> 
> Thanks, that works. Unfortunately, DejaVu Sans Mono looks too heavy in 
> my document: 
> is there a light variant? 
> 
> Also, can't the fallback mechanism be used? 
> Yes it can but you have to enable your custom typeface with 
> \setupbodyfont which
> wasn’t done in your example.

You're right, but I have done it in my original document.
Even with that, the fallback symbol does not show up:

\usemodule[vim]
\definefontfamily    [slidesfont][mono][Latin Modern Mono Light]
\definefallbackfamily[slidesfont][mono][DejaVu Sans Mono][range={"0222A}]
\definevimtyping[pascal][syntax=pascal]
\setupbodyfont[slidesfont]
\starttext
\startpascal
 X := Y ∪ Z;
\stoppascal
\stoptext

Nicola