The batteries also provide protection against no-voltage conditions, when they kick in to keep your gear running during temporary outages or for safe shutdown during longer power outages. Line voltage is indicated on the front panel’s blue flourescent display.
The APC S15’s noise filtration is so good that it renders background noise invisible and inaudible. It has been the cornerstone of my home theater system for 18 months, proving itself well engineered and highly reliable. Don’t start a movie without one. TPV