This counts BTUs received over the internal cell bus that were discarded because they contained detected errors, serving as this card's overall internal-bus error tally alongside the more specific cardInErrorBtus counter tracked elsewhere. A steadily climbing count here, especially when correlated with cardIncompleteFramesFromBus rising in tandem, strengthens the case that the fault lies in this card's physical connection to the backplane, such as a loose or corroded connector, rather than in any single external line or circuit. For example, cardBTUsBusErrors and cardIncompleteFramesFromBus both climbing together after a chassis was serviced points strongly to that card's backplane connector having been disturbed during the work.