just a complement to Robert's excellent answer...<br><br><div class="gmail_quote">2009/1/16 Robert Woodcock <span dir="ltr"><<a href="mailto:rcw@debian.org" target="_blank">rcw@debian.org</a>></span><br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div>On Thu, Jan 15, 2009 at 07:35:02PM -0500, Eric S. Raymond wrote:<br>
> The source of my confusion is this. I learned years ago to<br>
> distinguish between three categories of product:<br>
><br>
> 1. Line conditioners (LCs) and surge suppressors. The are just spike<br>
> filters, with no battery.<br>
><br>
> 2. SPS = Standby power supply. These normally filter mains power,<br>
> switching to a battery when the mains have a dropout.<br>
><br>
> 3. UPS = Uninterruptible Power Supply. These continuuosly feed power<br>
> to a battery, which discharges continuously to run the equipment.<br>
> When the mains go down, the battery stops charging.<br>
><br>
> My problem is this: The way these products are now labeled, I<br>
> could not work out a way to tell which are which. Some look so<br>
> small that they almost have to be mere line conditoners, because<br>
> there;s no room in the case for a serious battery pack. Others<br>
> could be SPS or UPS devices, but I can't tell which. All are now<br>
> just labeled "Battery Backups"!<br>
</div></blockquote><div><br>the situation is a bit more complex since, as most technologies, UPS have evolved over the time.<br>These devices now includes:<br>- offline systems (what you call SPS): this used to be so, but has evolved with AVR system most mfr now provides<br>
- line interactive UPS (what you call UPS)<br>- and online UPS<br><br>check <a href="http://en.wikipedia.org/wiki/Uninterruptible_power_supply" target="_blank">http://en.wikipedia.org/wiki/Uninterruptible_power_supply</a> to understand the difference between line-interactive and online systems.<br>
<br></div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><div><br>
> 1a: Does anyone have good heuristics for telling the LCs, SPSes,<br>
> and UPSes apart based on the packaging or the specs visible on them?<br>
<br>
</div>These categorizations are still useful today, although your terminology<br>
is different.<br>
<br>
If they have a battery, they are #2 or #3. If not, they are #1.<br>
<br>
Some of the fancier ones in category #2 are "line-interactive", which<br>
try to buck or boost voltage to maintain output compliance without<br>
going on battery. But they still pass whatever hiccups get through<br>
the filter to your equipment. You may or may not see any that do this<br>
for under $200. They'll use words like "line-interactive", "buck/boost",<br>
"AVR", etc., in their specs.<br>
<br>
UPSs of type #3 are commonly referred to as "online" or<br>
"double-conversion". Good luck getting anything like that for $200.<br>
APC doesn't even have one in their lineup (as far as I can tell, the<br>
entire Smart-UPS and Back-UPS line is #2).<br>
<div><br>
> When I last seriously examined the market (mid-2005), SPS designs<br>
> appeared to be on their way out because the switching electronics for<br>
> full UPS operation were dropping in cost fast enough to make SPS<br>
> designs a pointless economy. In the 2005 and 2007 revisions of the<br>
> UPS HOWTO, I must have believed SPSes were one with the dust of<br>
> history, because I didn't mention them anywhere.<br>
<br>
</div>Unfortunately they'll always be cheaper to make, and more compact.<br>
Since SPSs pass a fixed amount of energy through their inverter,<br>
they can get away with using a block of metal for a heat sink, instead<br>
of using active cooling.<br>
<br>
(This is a big reason not to hack external batteries onto a UPS that<br>
isn't designed to attach to them.)<br>
<div><br>
> I'd still believe that, except that it's 2009 and I saw at Ardmore<br>
> that APC is still selling not only units with serial-port interfaces<br>
> but units that I know for a fact have the old-fashioned single-pin<br>
> dumb interface. And if they're still selling *that* kind of obsolete<br>
> crap, I have to think maybe there are still SPSes in the world.<br>
><br>
> 1b: Is the SPS in fact dead as a technical category? If not, why not?<br>
<br>
</div>I'd say it's more pervasive now than in 2005. Price/profits/ignorance.<br>
<div></div></blockquote><div><br>it also seems that APC has based a part of its business on the cables, which enables a dumb or smart communication.<br><br>the dumb comm only applies to a few UPS manufacturers now, and possibly more to cheap units.<br>
<br></div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><div>
> Oh, and this, too:<br>
><br>
> 1c: RS232C, on consumer devices, in 2009? Ferfuckssake, *why*?<br>
><br>
> It's not like USB chips are expensive or anything. I know all about<br>
> this from GPS-land, actually; pl2303s are so cheap that even if the<br>
> vendors wanted to retread their RS232 designs, the cost of goods to<br>
> refit them with USB-to-serial conversion is close to zip. Does anyone<br>
> have a clue why this interface type didn't die five years ago?<br>
<br>
</div>Because the stuff they're currently selling is based on 5+ year old<br>
designs. Same reason why if you buy an alarm system or fire system,<br>
you get, among other things, a circuit board with gobs of discrete<br>
components on it.<br>
</blockquote><div><br>and more generally to address the legacy unix (HP-UX and IBM AIX) at least
market, which still doesn't support USB that much. This note also
applies to some BSDs. The only one that has evolved is Solaris...<br><br>Some will argue that AS400 also needs this kind of interface.<br><br></div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Ethernet interfaces are similarly cheap (< $3). Unfortunately, the<br>
products weren't initially designed with them in mind, so what you<br>
get for your $100-$300 is a computer on a card that has an ethernet<br>
port on the back.</blockquote></div><br>the problem here is that SOHO market generally need 1 UPS to protect 1 system.<br>using a point-to-point technology make it simple ; using multipoint techno like ethernet, wifi... make it harder.<br>
though it's still feasible and even considered, there is more complexity for the average user...<br clear="all"><br><my 2 cents here><br>Arnaud<br>-- <br>Linux / Unix Expert R&D - Eaton - <a href="http://www.eaton.com/mgeops" target="_blank">http://www.eaton.com/mgeops</a><br>
Network UPS Tools (NUT) Project Leader - <a href="http://www.networkupstools.org/" target="_blank">http://www.networkupstools.org/</a><br>Debian Developer - <a href="http://people.debian.org/%7Eaquette/" target="_blank">http://people.debian.org/~aquette/</a><br>
Free Software Developer - <a href="http://arnaud.quette.free.fr/" target="_blank">http://arnaud.quette.free.fr/</a><br><br>