Does UPS work as a voltage stabilizer?

My UPS has been having a problem, and about a month ago, I found that 'my' UPS was not working as a voltage stabilizer. But I don't know if UPS is generally designed to work as a voltage stabilizer. Is it?
Well, they are designed so that if the voltage goes above or below a certain voltage, it switches to battery. There are some others that they try to adjust the voltage, and then switch to battery if it is out of range. Mine is a stabizer, and is an APC Back-Ups XS 1200.
they are usually stabilisers aswell they maintain a specific voltage and if you get a brown out ( drop of more than 10% required voltage) the battery kicks up until everything is normal again.