question #1 Sahih Muslim 378b, Book 4, Hadith 3 : What methods were considered by the Companions to announce the timings of prayer?

They (the Companions) discussed that they should know the timings of prayer by means of something recognized by all. Some of them said that fire should be lighted or a bell should be rung. But Bilal was ordered to repeat the phrases twice in Adhan, and once in Iqama.