When a subsystem must function under certain conditions, it is helpful to describe the conditions. Conditions may include environmental parameters, engineering requirements, and/or machine performance specifications (i.e., operating temperature, capability, cycle time, mean-time-between-failure (MTBF), mean-time-to-repair (MTTR) or other measurable engineering attributes).
The function(s), conditions and requirements of the subsystem being analyzed. When the subsystem has many functions with different potential failure modes for each function, list each function separately.