The circuit drawn pertains to a regular industrial UPS (Uninterruptible Power Supply), which shows how the batteries take control during an outage in electrical supply or variation beyond the normal limits of the voltage line, without disruption on the operation providing a steady regulated output (5 Volts by LM7805) and an unregulated supply (12 Volts).

The input to the primary winding of the transformer (TR1) is 240V. The secondary winding can be raised up to 15 Volts if the value is at least 12 Volts running 2 amp. The fuse (FS1) acts as a mini circuit breaker for protection against short circuits, or a defective battery cell in fact. The presence of electricity will cause the LED 1 to light. The light of LED will set off upon power outage and the UPS battery will take over

The circuit was designed to offer more flexible pattern wherein it can be customized by using different regulators and batteries to produce regulated and unregulated voltages. Utilizing two 12 Volt batteries in series and a positive input 7815 regulator, can control a 15V supply.

Industrial UPS are generally categorized as:
Standby – battery backup and surge protection
Line Interactive – variable-voltage transformer and regulates the input AC voltage
Online – supplies all or at least a part of the output power