: ▁This ▁variant ▁is ▁used ▁as ▁a ▁command ▁vehicle , ▁generally ▁as ▁a ▁T act ical ▁Oper ations ▁Center ▁( TO C ). ▁The ▁passenger ▁compart ment ▁is ▁raised ▁to ▁ 7 4 . 7 5   in ▁( 1 8 9 . 9   cm ). ▁The ▁compart ment ▁has ▁a ▁commander ' s ▁h atch ▁with ▁no ▁weapons ▁mount ▁or ▁vision ▁blocks . ▁A ▁tent ▁is ▁carried ▁on ▁the ▁top ▁rear ▁and ▁attach es ▁directly ▁to ▁the ▁rear ▁of ▁the ▁track ▁to ▁provide ▁greater ▁work ▁space . ▁Multiple ▁M 5 7 7 s ▁can ▁be ▁connected ▁via ▁the ▁t ents ▁to ▁form ▁a ▁larger ▁operations ▁center . ▁An ▁additional ▁fuel ▁tank ▁is ▁mounted ▁in ▁the ▁right ▁rear ▁of ▁the ▁compart ment . ▁Long - range ▁communic ations ▁is ▁exped ited ▁by ▁the ▁use ▁of ▁a ▁hand - c rank ed ▁extend ible ▁anten na ▁system . ▁A ▁ 4 . 2   k W ▁auxili ary ▁power ▁unit ▁( AP U ) ▁is ▁mounted ▁on ▁the ▁right ▁front ▁of ▁the ▁vehicle ▁to ▁provide ▁ 2 4   vol t ▁power . ▁The ▁A PU ▁can ▁be ▁dis mount ed ▁using ▁a ▁dav it ▁( c rane ) ▁carried ▁on ▁board ▁and ▁sand bag ged ▁for ▁noise ▁supp ression . ▁A ▁single ▁A PU ▁can ▁provide ▁power ▁for ▁two ▁M 5 7 7 s . ▁The ▁compart ment ▁includes ▁features ▁such ▁as ▁map ▁bo ards , ▁fol ding ▁tables , ▁radio , ▁computer ▁terminal s ▁and ▁other ▁command ▁and ▁control ▁equipment .