Pronouncing the Adhan twice for the Fajr prayer is an act of the Sunnah (whatever is reported from the prophet). One Adhan should be pronounced before the appearance of Al-Fajr-ul-Sadiq (true dawn) to alarm the people to the forthcoming due time of Salah (Prayer) and another after the appearance of Al-Fajr-ul-Sadiq. (Part No. 5; Page No. 57) The Mu'adhin (caller to Prayer) adds to the second Adhan the phrase "Al-Salah Khayrun min-al-Nawm" twice after the two phrases "Hay `ala Al-Salah (come to Prayer)" and "Hay `ala Al-Falah (come to success)".May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.