The same as any surge arrestor equipment - to prevent surges from damaging the (telecom) equipment.
negative polarity is achieved by grounding the positive terminal of power supply system and the battery bank. This is done to prevent electolysis depositions.
what indicates the power supply sending steady power to the system board
A device, composed of sharp points and/or knife edges, that discharges powerline overvoltages to ground. The term lightning arrestor is a misnomer, as these devices cannot protect against a direct strike to the powerline!
because the power still are in circuit of the motherboard and you have to drain the system
Dual power supply is used to describe a computer system with two power supply units (PSU's). This is to provide extra power for the computer's internal components.
the power supply whines when you first turn on the system
The GameCube's power supply is internal. The whole system is very easy to transport.
IPS is instant power supply that is a backup system that start when main energy not available.
Most often, power supplies for any type of equipment is givin to you when you buy what the power supply is for.
It connects the drive to the system power supply.
The electric voltage are energy to my system.
One place is in telecommunication racks, where AC power needs to be converted to DC to power the telecommunication equipment. And their are plenty of other applications as well.