Kent County commissioners unanimously approved $46,751 Tuesday to replace a failed backup power system that supports 9-1-1 operations and critical county infrastructure. The uninterruptible power supply, installed in 1989, finally failed after more than three decades of service, said Pete Landon, director of the county’s emergency services office. The system provides backup power to radio systems connecting the 9-1-1 dispatch center to county network infrastructure, the detention center and sheriff’s office.