The hardware is normally supplied by the mains and the UPS will only take over in the event of a power cut or major drop in voltage.
Off Line technology enables the hardware it protects to be powered long enough for data backup to be made and/or to turn off the appliances correctly.

This switch to battery power takes a certain time (switchover in general >4ms) which will not be troublesome for computers with a switching power supply, but it could cause a problem for more critical hardware (measuring instruments).

Off Line UPSs are the most economical. They are recommended for mono-station computers (PC type) dedicated to office systems or gaming and small servers in an electrical environment with few disturbances such as an agglomeration.

The Off Line technology principle is improved since the input voltage is regulated and filtered by the UPS before being delivered to the hardware.

The power supplied is therefore of better quality. A voltage regulator enables the continuous supply of quality power when major variations occur and without using the batteries whose wear is directly proportional to the number of charging cycles. A filter and surge protector increase the level of safety.

When a power cut occurs, the UPS switches to battery mode (switchover time <2ms) and a communication software takes charge of files backup and program shutdown.

Line Interactive technology is recommended in areas where the mains power is moderately disturbed (commercial or rural areas) and also is chosen to protect servers, CAD and minor accounting systems.

The UPS supplies uninterrupted power, thereby ensuring constant and disturbance-free voltage. The device to be protected is therefore totally disconnected from the mains, which means there is no switchover time and no power disturbances.

When a mains power cut occurs a communication software automatically closes all programs after having performed the required backups.

Tests show that these On Line UPSs offer the most stable output power and the best immunity to interference.

The On Line technology is particularly recommended in industry. It is also chosen to protect the systems where even the most minor loss of data is unacceptable such as calculators, PLCs, cash registers or major IT systems for example and in a more general way any strategic application, critical electronic system and medical apparatus.