The UPS is an abbreviation of English word uninterruptible power supply.

The uninterruptible power supply is a device that supplies energy to connected appliances from own built-in accumulator after the mains failure. The source circuits change direct voltage of the accumulator to alternating voltage. The battery is lead, sealed, maintenance-free. It is directly built into the cabinet of the power source.

The uninterruptible power supply operation is automatic – transition to the back-up mode after the mains failure and vice versa after the mains recovery, accumulator recharging. User is not burdened with the power source operation.

Following statistic analysis in power engineering, only twenty percent of the mains failures take more than ten minutes. From this reason the basic back-up time ranges about ten minutes. This enables to cover the majority of the mains failures.

Besides the back-up the power source has also other functions. They contain mains disturbances suppression, output voltage stabilizing and galvanic isolation.

Indication of the source operation is acoustic and optical. User is warned of transition to the back-up mode and in advance of the back-up termination at battery discharging. This enables to end operation of supplied devices in time.

In case the PC supply is backed-up, the communication between the PC and the power source is possible. The PC is automatically informed about the mains failure and the back-up termination. Software package provides execution of all actions necessary for regular system shutdown. Communication software varies according to the type of the operation system.