Primary and secondary apparatuses avoid concurrent performance of activities, wherein the secondary apparatus has a best and possibly different worst case minimum amounts of time required to perform activity. The primary apparatus ascertains a first future moment when it will become inactive and ascertains whether its upcoming period of inactivity will not be less than the secondary apparatus' best case minimum amount of time required to perform activity. If not, the primary apparatus asserts, in advance of the first future moment, an inactivity indicator signal indicating its upcoming inactivity. The interval between assertion of the inactivity indicator signal and the first future moment is greater than or equal to a difference between the secondary apparatus' worst and best case minimum amounts of time required to perform activity.