I have to ask this question beside this is offtopic, but I trust in members experience here, so I hope admins won't be angry.

At each AP we use UPS'es PowerMust 800 USB. I know it's cheap and not perfect, but it saves our machines from short electricity blackouts and protects from overload (and it's cheap). However, when there is some electricity overload or some disorder, I don't know, it turns off because of protection and then we have to go at the place and turn it on. And if we have to climb 5 times per year to some tower to turn the UPS on, it's not fun anymore. It's not a problem at some AP's which are easy to reach and some have stable electricity, but we have few positions with electriticy problems (one at electrical plant, for example, which has very unstable industry electricity for internal use in the plant itself). It doesn't hurt huge electrical engines and light bulbs, but it makes trouble to computers.

I am thinking about some APC model to put at some AP's where we have most problems. Does APC handles this better? I mean, does it turn off ever or is it always on? If there is some disorder in voltage or something, it should just turn on battery power and then when voltage stabilize, it should switch back to that supply. So, UPS should never stop in my opinion. How about APC models?

I am thinking of smaller model like APC BK350EI and APC BK500EI? What is your experience with these? Or do we have to get some smart model?

You should have the UPS at the base of the tower where your POE goes up.

You get what you pay for with UPSs, APC are better.

I have PC's, not POE and RB, so UPS-es are up on the towers also. It's no problem to get APC UPS'es for these few points with problems, but will APC do the job? Without stopping? And what model, smart, back or what?

Maybe you could use something like this to move your UPS's to the base of the tower ?

http://www.ramelectronics.net/html/EXT-RS232.htm

Many of the smaller, cheaper APC UPS units have the same basic issue. Once the battery runs flat, the unit requires manual intervention to switch back on. We've also found the reliability of the low-end APC units to be less than stellar. In fact, our last one in the field we replaced just 2 weeks ago, having found it emitting a pathetic sheep-like bleeting sound with dimly lit pilot light and no power to the outlets. Fully a third of the small ones we purchased failed within 3 years. Note to APC: UPS is supposed to --enhance-- reliability.

Look for "auto restore" or some such language in the product description before buying.