 An active sonar system was scheduled to be installed in June 1940 , but it is uncertain when it was actually done . During the war , the ship 's light anti @-@ aircraft armament was augmented several times . Improved 2 cm C / 38 guns replaced the original C / 30 guns and three additional guns were added sometime in 1941 . The two guns on the aft shelter deck were replaced by a single 2 cm quadruple Flakvierling mount , probably during her late 1941 refit . Richard Beitzen appears not have any additional AA guns added after this time . 
