M bit / s . ▁The ▁ST 4 1 2 HP ▁R LL ▁variant ▁aver ages ▁ 1 . 5 ▁data ▁bits ▁per ▁transition ▁for ▁a ▁data ▁rate ▁of ▁ 7 . 5   M bit / s ▁ ▁Interface ▁to ▁controller ▁▁ ▁In ▁the ▁ST 5 0 6 ▁interface , ▁the ▁drive ▁connect s ▁to ▁a ▁controller ▁card ▁with ▁two ▁rib bon ▁c ables ▁carrying ▁signals , ▁while ▁a ▁third ▁cable ▁provides ▁power . ▁ ▁The ▁two ▁signal ▁c ables ▁are ▁the ▁wide ▁ 3 4 - pin ▁control ▁cable ▁and ▁the ▁narrow ▁ 2 0 - pin ▁data ▁cable . ▁ ▁The ▁control ▁cable ▁interface ▁is ▁very ▁similar ▁to ▁the ▁standard ▁Sh ug art ▁flo ppy ▁disk ▁interface ; ▁like ▁that ▁flo ppy ▁disk ▁interface , ▁it ▁can ▁support ▁four ▁drives . ▁ ▁The ▁data ▁cable ▁car ries ▁a ▁read ▁signal ▁and ▁write ▁signal , ▁both ▁as ▁differential ▁binary ▁signals : ▁the ▁two ▁signal ▁states ▁correspond ▁to ▁the ▁two ▁possible ▁differential ▁signal ▁polar ities . ▁The ▁data ▁represented ▁by ▁these ▁signals ▁is ▁M FM , ▁so ▁the ▁absolute ▁signal ▁states ▁are ▁not ▁significant : ▁the ▁data ▁is ▁represented ▁in ▁the ▁timing ▁of ▁the ▁state ▁trans itions , ▁like ▁in ▁flo ppy ▁disk ▁systems . ▁While ▁up ▁to ▁four ▁drives ▁can ▁share ▁a ▁control ▁cable , ▁each ▁drive ▁has ▁its ▁own ▁dedicated ▁data ▁cable ▁connecting ▁it ▁to ▁the ▁hard ▁disk ▁controller ▁( H DC ). ▁ ▁( M ost ▁H DC s ▁supported ▁only ▁two ▁drives .) ▁ ▁The ▁control ▁card ▁transl