On-Line UPS systems can be safely maintained while still providing continuous power to connected equipment. However, most Line-Interactive UPS systems cannot. The difference is in the On-Line UPS's power bypass feature. If an On-Line UPS experiences an internal fault or overload, it will automatically "bypass" its internal components and deliver power directly to connected equipment. In addition, On-Line UPS systems feature an external bypass switch that allows users to perform the same function manually. While select Tripp Lite Line-Interactive UPS systems are being introduced which feature an automatic internal bypass function, none feature a manual external bypass switch.