It has already been translated as follows (medium confidence, however, since I'm not quite sure this is the best solution).
HTH

The images that we have defined as "alarm bell images" (39.3%) have another purpose, however: these are images that are imposed, service after service, and which refer immediately to a determined subject. There are cases of crime stories to which many services are dedicated, like the Cogne murder or the story in which Erica and Omar were involved, or in the case of "hot topics" often reproposed, like, for example, the nude and undernourished African children used to evoke the theme of world hunger. In these cases, specific images are shown, which immediately refer to the subject treated and which have the main function of illustrating the matter being presented
http://www.segretariatosociale.rai.it/inglese/palinsesto/dos...


By contrast, alarm bells are meant to steal attention; to command interest, assert an urgent need, and force someone to do something. Anyone have a casino that advertises in their town? They're a good example.

Advertisers who believe in the alarm-bell approach want their advertising to be intrusive and attention-getting, so they do everything they can to get the audience's notice. They believe that if they can make the offer good enough, the pitch loud enough, the case compelling enough, people will be bound to do business with them.
http://www.businessweek.com/smallbiz/content/sep2006/sb20060...