The CGS59 is a Serge inpired multi-stage sequencer. Unlike most sequencers, this one makes no use of binary counters. Rather, it uses a set of individual stages, each one directly accessible. As such it could be considered to allow "random access".
One CGS59B is required for each Programmer/Sequencer unit. One CGS59A for each step in the unit eg a 4-step unit = 1x CGS59B + 4x CGS59A, an 8-step unit = 1x CGS59B + 8x CGS59A
See the CGS87 for a more generic PCB design
CGS59 Datasheet and Build Guide