French phrase
Faites-moi ~ si ~.
Meaning
Give me ___ if ___.
When to use it
A polite request to be informed if something happens. It is common in everyday speech and suitable for addressing superiors.
Example dialogue
Faites-moi signe si vous arrivez.
Give me a sign if you arrive.
D'accord, je vous préviendrai.
All right, I'll let you know.