The UPS is meant to only give you sufficient power to either help you switch on the alternate power like a generator / alternator or save your work and shut down the system that you are working on. When one is quite engrossed in his / her work one may not notice that the main power has failed and will continue to work with the UPS power if there are no indications.

This is where the necessity of a warning comes up. Standard UPS incorporates both audio and visual warnings for the user to understand that the power is being consumed form the battery and not from the main line.

Visual warning:

There are UPS that have one LED, two LED's and three LED's. For UPS with a single LED, the LED glows a green color, indicating the system is working on the main power line. When the power fails, the LED turns either amber or a red with blinking at an interval of thirty seconds indicating that the UPS is working with back up power; power being supplied from the battery that is in the UPS. After for a particular duration of time and if by then the power is not restored by switching on a generator / alternator, the light turns a bright red along with continuous blinking indicating that you have a critical two minutes left for the power of the battery to drain out and crash abruptly.

For UPS with two LED's the green is a solo type indicating mains; and the type, then only one green light is visible. If the UPS is having two lights then the green LED is ?ON? and the other LED is off indicating main power line consumption. When the power main power fails, the other LED i.e. either a red or amber comes on indicating the power is of last two minutes. This is accompanied by continuous blinking of the LED indicator.

For UPS that have three LED's , the green indicates UPS working from main lines, the amber

indicates the UPS working from battery back up and the red LED indicates UPS working from

critical backup. As mentioned in the UPS with two LED's the blinking of the UPS is the same

here too. For back up it is blinking at the rate of thirty seconds per blink and for critical power it is blinking at the rate of almost one second per blink.

Audio warning:

Almost all UPS have an audio warning incorporated into the circuit. The audio warning is a beep, which during critical back up power being consumed the beep is continuous with a frequency that is equal to the blink rate. The audio warning gives one an indication that it is high time you shout down your UPS after saving critical data.