question #1 Sahih Muslim 1092a, Book 13, Hadith 42 : What is the significance of the Adhan in determining the time for starting a fast during Ramadan?

Bilal would pronounce Adhan (at the fag end of the night in order to inform the people about the time of the Sahri). So you eat and drink till you hear the Adhan of Ibn Umm Maktum (which was pro- nounced at the conclusion of the Sahri and the commencement of the fast).