Bilal Bin Rabah was the companion of Prophet (PBUH) born 580 CE. He has the title of being the first Moazzin of Islam.
Bilal Bin Rabah was an Ethiopian slave. He secretly converted to Islam but when his master knew about it, he gave him severe physical punishments but he steadfast to his belief. Abu Bakar (R.A) bought him from his master and set him free.
Whenthe pattern of Adhan was selected, then Prophet (PBUH) appointed Bilal to say the first Adhan. During the life of Prophet (PBUH) Bilal was the one who said Adhan. However, after the Prophet (PBUH) passed away, Bilal gave Adhan only once when he traveled back from Syria.
Bilal died in Damascus in 640 CE.