[mythtv-users] Uninterruptible Power Supply

David Brodbeck gull at gull.us
Tue Dec 22 18:19:55 UTC 2009

On Dec 21, 2009, at 11:19 PM, Raymond Wagner wrote:

> On 12/22/2009 2:09 AM, Jerome Yuzyk wrote:
>> From times I've had a monitoring UPS (or
>> bothered to set up monitoring), living in older houses, or even
>> apartments, power can vary widely around 120VAC. A nice battery  
>> smoothing
>> out those variances can help your electronics last longer.
> UPSs are generally passive systems.  That means the battery is kept  
> charged offline, and only swapped into place during a power outage.   
> The unit itself only ends up having a couple milliseconds of power  
> left internally to allow the transfer without interruption of  
> power.  While active systems do exist, they are only ever used for  
> very large systems designed for server rooms, and significantly  
> shorten the life of the batteries.

I actually had a desktop-sized one, for a while.  It was manufactured  
in the 1980s and was designed to fit underneath a monitor (deep, flat  
case.)  It was a true "online" UPS, with the incoming line power only  
charging the batteries.  I eventually got rid of it because the  
constant inverter noise was quite annoying.

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