 In the great fire of 1405 , the tower burnt out completely . It suffered severe structural damage that required thorough repairs , which were not complete until after the last restoration in 1983 . The prison cells were abandoned and a clock was first installed above the gate in the early 15th century , probably including a simple astronomical clock and musical mechanism . This clock , together with the great bell cast in 1405 , gave the Zytglogge its name , which in Bernese German means " time bell " . 
