Offline UPS system channels the incoming mains power, via a filter, directly to the load. As soon as the incoming power is outside tolerance, the UPS switches to battery operation.

On Line-interactive UPS system channels the incoming mains power, via an AVR-automatic voltage regulator, directly to the load. Compared to off-line, the system can handle much larger voltage before switching to battery operation.
1PHASE OR 3-PH
PHASE AUTO SERIES TYPE
3-PHASE ISOLATION TYPE