Muezzin

A muezzin is a man who calls Muslim people to prayer through the adhan from the minaret of a mosque. 
He leads the call ("adhan") to Friday service and the five daily prayers (also known as the salat) from one of the mosque's minarets. Blind people often got the position; this is so that they could not see the places where women gathered. Today, many mosques have electronic amplification, and the muezzin no longer needs to be on the minaret. 
In the city of Abu Dhabi, the call to prayer is coordinated, all mosques transmit the call of the muezzin of Sheikh Zayed Mosque. The idea for a similar system in Cairo failed in 2004.