Something seems slightly missing in this discussion here, grin!   
      
   ML>BR>Mine doesn't click, it just beeps like mad when I lose power lol   
      
   ML>  UPS == Uninterruptible Power Supply   
      
   ML>over-voltage...   
      
   ML>UPSes DO have relays in the   
   ML>for when they switch to their batteries... other UPSes choose to use   
   ML>solid-state relays for their switching... all of my    
   ML>APC UPSes have relays an   
   ML>always have had them...   
      
   I've used nothing but APC -> Smart <- UPS equipment for years and years now.   
   The reason is that you need to very carefully choose the 'Smart' version is   
   that remember your power line service is alternating current, AC, service. It   
   is sine wave service where, per Tesla's contribution to this stuff way, way   
   back, the voltage goes back and forth from positive to negative in a smooth   
   waveshape so that we all can use pig iron transformer operations for   
   everything from the monsters you see in the power substation yards down to   
   even tiny ones in, say, five watt short wave ham transmitters and receivers.   
   Or .. in my case my hand designed and personally built KW CW amps that helped   
   me be the only person ever in the history of ham radio to apply for a 300   
   country original ARRL DXCC award only on 40 meter telegraphy.  The same band   
   and equipment I used to kill the original Russian Woodpecker OTH radar and get   
   it out of the ham bands for all us even EOC folks back in the mid-1970's.   
      
   The key is that when you are really 'protecting' any AC equipment like all   
   this, think a bit.  Poof, power goes off!  OK, your UPS has to generate and   
   turn on AC power exactly at the same 60 or 50 hertz frequency that you   
   normally use.  Plus do it fast enough so there is no interruption for the   
   critical equipment and service it is protecting.  Slow forward now. OK, your   
   normal power service comes back on.  But wait!  You ABSOLUTELY have to match   
   the new 'normal' sine wave shape and frequency to your UPS service sine wave   
   and frequency.  Or BOOOOOOM, the two electrical sources will fight with each   
   other and even blow up something like your whole equipment.  And a simple   
   RELAY can do this??  Not a chance.  Your UPS absolutley has to move the   
   emergency service wave form to the EXACT timing and shape of the replacement   
   standard power source!  That is exactly what a 'SMART' UPS does.  So you don't   
   blow up this or that which is plugged into it.  This can get a lot bigger.   
      
   A 'UPS' ain't at all what a backup or replaced or added electric generator is   
   for the or multiple power companies need is it?  Absolutely necessary is a way   
   to perfectly match the phase and waveshape of any new generator AC power   
   source to the or a 'grid' line operation when it touches it!  Because if you   
   don't, you can blow up the whole generator operation if you don't absolutely   
   match it to the souce line it is being attached to!  Couple of interesting   
   little facts I know about such life.  In the early 1950's when I was in the   
   8th and 9th grade here in school at College Station, Texas, besides the local   
   cops, the State police, and the Texas A&M cops, the campus cops that were KK's   
   to us, I also maintained the radio for Mr. Frank Brown's wrecker trucks. For   
   which he let me drive them even back in early high school here, grin! What I   
   did learn from him was that his father was one of the engineers for the Texas   
   Aggie electric power plant on the campus!  They expanded the plant and put in   
   a new added major generator.  But got the wires crossed on the oscilliscope to   
   use to change the rotation speed on the new generator to gently synchronize   
   it's phase to match the power line operation of the major operations.  Perfect   
   match on the screen!  They threw the switch to bridge it to the system!    
   BLAMMMMM!  It blew the whole new generator off the concrete table and totally   
   ruined it!  But wait!  There's more!   
      
   My best friend at the time of my first degree from Texas A&M had a double   
   degree in electrical and mechanical engineering.  His real to this day special   
   interest and capability is in hydraulic engineering.  However, a decade or so   
   after he and I graduated in 1965, he went to work for a major power company   
   out in West Texas.  He wasn't in charge of the particular expansion of the   
   generator service out there for all Abilene and so on, but was watching over a   
   completely existing generation plant when the new one was being added to the   
   grid.  Guess what?  Exactly the same thing happened out there in West Texas   
   that I had decades before learned about happened at Texas A&M College!!  The   
   error completely blew up the new megawatt generator, blew the bolts apart and   
   hurled it off it's complete mounting pad.  No, my friend Mike Clifford was   
   *NOT* involved at all in being responsible for any of this. However, as we   
   were both already in the 1970's VERY famillar with what a single atomic bomb   
   could do to the power grid and every copper wire connected electric system for   
   even the whole USA from one bomb and that even the solar flares could really   
   be worse, he made the decision to leave the electical industry and not ever be   
   involved in this or that phase error issue, if at all possible.  Both of us   
   were even back then completely aware of the Carrington Event Solar Flare in   
   1869, two years after the the Golden Spike was driven here in the USA on the   
   railroads that joined the East and West Coast.  Which burned up all of the   
   telegraph operations in the whole USA.  Killed three Morse Code operaters that   
   were sending code and put some 23 more in hospitals when it hit!  And where   
   the EMP wave hit the railroad rails as it arced from them to the ground where   
   this stuff goes, in six places it even set the wood cross ties on fire!   
      
   Yes I learned a LONG time ago to NEVER use a UPS that was not a SMART UPS and   
   further to NEVER use a UPS that did not have an internal pig iron power   
   transformer to really protect you from nasty power surges.  Plus make sure   
   that when it bridged to the return of normal power. the phase was matched   
   between everything.  Thank you SMART APC!   
      
   Mike Luther N117C at 1:117/100   
      
   ---   
    * Origin: BV HUB CLL(979)696-3600 (1:117/100)