Replace images by icons

In that case, the inner quotations marks should be backslashed:

COM_JEM_ICAL_ICON="<span class=\"icon-calendar\"></span>"
COM_JEM_EMAIL_ICON="<span class=\"icon-mail\"></span>"
COM_JEM_PRINT_ICON="<span class=\"icon-print\"></span>"

is there a possibility to do near the same with fontawesome?

That should be easy: search for "Icon-" in the css files of your template, find the ones you want to use for print, mail and calendar and use their declarations instead of mine in the language override.

Thanks, I just tried, but this seams not to work with fontawesome

I remember vaguely that fontawesome uses s.th. like "fa-" in its css (not "icon-"). Maybe that helps you to find s.th. like "fa-print" as icon font.

What I don't understand: Why you use language overrides instead of adding the <span> directly to the code, giving a class so it can be styled via css?

It should be something like that:
.jem-print-icon {
content: "\f02f";
}
As far I know, all Icons can be "encoded" with such a string.

is this @jojo12 or @HerKle
I think HerKle is trying to separate icons from the output.class.php to be more free! Because you can't override output.class.php