 O 'Brien was also equipped with four twin 21 in ( 533 mm ) torpedo tubes . The General Board of the United States Navy had called for two anti @-@ aircraft guns for the O 'Brien @-@ class ships , as well as provisions for laying up to 36 floating mines . From sources , it is unclear if these recommendations were followed for O 'Brien or any of the other ships of the class . 
 O 'Brien was also equipped with four twin 21 in ( 533 mm ) torpedo tubes . The General Board of the United States Navy <a href='been_done' title='1'><mark>had</mark></a> called for two anti @-@ aircraft guns for the O 'Brien @-@ class ships , as well as provisions for laying up to 36 floating mines . From sources , it <a href='drop_aux' title='2'><mark>is</mark></a>unclear if these recommendations <a href='uninflect' title='3'><mark>were</mark></a> followed for O 'Brien or any of the other ships of the class . 
O 'Brien was also equipped with 4 twin 21 in ( 533 mm ) torpedo tubes . The General Board of the United States Navy done called fir 2 anti @-@ aircraft guns fa da O 'Brien @-@ class ships , as well as provisions for layn up to 36 floatin mines . From sources , it unclear if dese recommendations was followed for O 'Brien or any of the other ships of tdaclass .