This circuit can be primarily used for charging 12V Ni-Cd battery packs. Any way 6V and 9V battery packs can be also charged
This is the circuit diagram of a simple UPS that can deliver 12V unregulated and 5V regulated DC.
Some time disturbance of power supply creates a number of problems. Especially in sensitive departments such as Radar System
An Inverter is a device that converts 12 volts dc to 120 volts ac, which is what we use in our homes.
So we can say that multi-voltages may be included in secondary that depends upon our requirements.