 The AL-FIU contained 8 simplex groups of 96 lines each, referred to as Analog Line Units (ALUs), controlled by a redundant controller, the Analog Control Unit (ACU).The 96 lines within each ALU were housed on 12 circuit packs of eight line circuits.These 12 circuit packs were electrically grouped into four groups of three cards, where each group of three cards shared a serial 24 timeslot PCM group.