This read-write enumerated integer sets how sensitive the ATS is to voltage fluctuations before deciding to transfer sources: high(1) for the tightest protection, low(3) for tolerating more frequent small line-voltage changes without switching. Admins tune this based on how transfer-sensitive their equipment is versus how much they want to avoid unnecessary source transfers for minor fluctuations. Setting this to low(3) on a facility with a naturally noisy but otherwise reliable utility feed avoids frequent unnecessary transfers over minor voltage dips.