French phrase
Faites-nous ~.
Meaning
Let us know ___.
When to use it
A request for information or a signal. Common in casual and professional settings, with a mildly imperative tone.
Example dialogue
Faites-nous signe quand vous arrivez.
Let us know when you arrive.
Pas de problème, je vous préviendrai.
No problem, I'll let you know.