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Date:      Wed, 16 Oct 2013 23:23:12 -0600 (MDT)
From:      Warren Block <>
To:        Erich Dollansky <>
Cc:        Frank Leonhardt <>,
Subject:   Re: UPS buying suggestion
Message-ID:  <>
In-Reply-To: <>
References:  <> <> <> <> <>

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On Thu, 17 Oct 2013, Erich Dollansky wrote:

> Hi,
> On Wed, 16 Oct 2013 22:12:24 +0100
> Frank Leonhardt <> wrote:
>> On 16/10/2013 03:43, yudi v wrote:
>> At the risk of going off-topic: as Warren has pointed out, not all
>> UPS units are the same. In fact, many units calling themselves a UPS
>> are actually backup power supplies, which switch over to battery if
> it is a rare event to see the on-line version here. Of course, they are
> much better when it comes to wave form and switch-over time. The wave
> form is very close to a sine wave and they do not have to switch over
> as they are always providing the power.

> But you also must see the cost. You loose about an extra 10% of
> electricity in the system. So, it is also a cost factor.

Online UPSs are rare and expensive everywhere.  Computer power supplies 
are not as sensitive as they once were, and the switchover time of 
standby UPSs is almost certainly adequate.

About sinewave output: 
shows oscilloscope screens for an APC Back-UPS, Smart-UPS, and line 
voltage, and talks about the differences.  Amusingly, the Smart-UPS 
provides a cleaner sine wave than comes out of the wall.

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