Breakdown of Le détecteur a déclenché l'alerte hier soir.
avoir
to have
le
him, it (masculine direct object pronoun)
hier
yesterday
le soir
the evening
Questions & Answers about Le détecteur a déclenché l'alerte hier soir.
Why is "last night" translated as hier soir rather than la nuit dernière?
What does the verb déclencher mean here, and is it only used for machines?
Déclencher means to trigger, set off, or initiate. While it is perfect for physical mechanisms like an alarm (une alerte), it is heavily used at the B2 level for abstract things too. You can use it for triggering a strike (déclencher une grève), a debate (déclencher un débat), or a strong emotional reaction.
The current lesson is about using en cas de. How could we apply it here to specify "in case of fire"?
You would add en cas d'incendie to the sentence. The phrase en cas de is followed directly by a noun with no definite or indefinite article. Because incendie (fire) starts with a vowel, de becomes d'.
Why must we use the passé composé (a déclenché) instead of the imparfait (déclenchait) here?
The time marker hier soir pinpoints a specific, completed timeframe. Because the triggering of the alert was a single, finished event that happened at that specific time, the passé composé is required. Using the imparfait would change the meaning to a repeated habit, implying the alarm used to trigger every evening.