Subject: Re: serial port control
To: Wolfgang Rupprecht <email@example.com>
From: Ted Lemon <firstname.lastname@example.org>
Date: 02/12/1998 14:28:48
> I was talking about a 60hz UPS, and the assumption is that the person
> designing the UPS isn't a total dork and is limiting the rise time to
> something reasonable. Further I assumed that they did a good job and
> didn't have horrible overshoot and ringing problems. In short I'm
> assuming that they didn't use the excuse of square wave output to hide
> all sort of sins.
This is probably not a good assumption. The watchword with the
square-wave-output UPS is typically "cheap, cheap, cheap!".
Thanks for the explanation of switching power supplies, BTW - I had
always wondered how they work. Two of my machines downstairs use
switching supplies; the other uses a linear supply, so I'm in a
slightly different situation than the average user. Also, I don't
think CRTs use switching supplies, do they?
Is it possible that a typical (cheap!) switching supply makes
assumptions about its supply that aren't valid if the supply produces
a square wave, and that this could cause the linear supply to behave
badly even though an ideal linear supply might love a square-wave
input? The reason I ask is that I have definitely heard of switching
supplies being fried by square-wave UPS's. Could be Urban Legend, I