Same run, downstream stopped. Transportation freezes as one unit; accumulation keeps absorbing zone by zone.
Moves product A to B at one speed. No queue. If something stops downstream, the whole unit stops with it. Sorters, transfers, diverters, belt curves.
Moves product and can also hold it, zone by zone, without pressure, when downstream isn't ready. It absorbs the gap between arrival and processing.
EZ in the name means accumulation with self-contained zone control. No EZ means transportation, all on, all off. Those two letters tell you the control architecture and whether you'll plan for Aux I/O. This naming is Hytrol's; every maker sells the same categories under its own letters. Category first, naming second.
Any point in a system where product may need to wait, before an induction, before a merge, before a scan point, before a manual process, before a sorter, before a pack station, before a dock door, is a point where accumulation must be evaluated.