Why spend $100+ for something when all that is required is a
$10 filter? But even worse, everyone has just assumed a
noise impulse has compromised an xDSL modem power supply. But
that power supply already has that filtering. More likely,
noise is being induced on the phone wire. For example, is his
phone wire twisted pair? Most older phone lines are not
twisted pair and therefore a excellent receptors of noise on
adjacent wires. That phone line bundled with wire to power
air conditioner and fan will carry noise impulses into the
xDSL modem. A $100+ UPS would do nothing to solve this
problem. What is the phone wire? Where is that phone wire
(and other household phone wires) run?
Then there is the question of how the xDSL modem connects to
AC. Does it use the third prong safety ground or is it just
an two wire connection. If it is a three wire power plug,
then poor connection on the household safety ground system
would result in another incoming noise path into the xDSL
modem. Again, the $100+ UPS would not address this problem
either.
Before seeking expensive solutions, maybe first learn the
reason for that problem? All this talk of $100+ UPSes for a
$10 filter sounds like everyone has too much money to burn.
> > "EldredP" wrote...
> > > > <snip>
> > > It dies when the AC goes OFF??? I'd expect just the opposite...
> > > If it's a momentary power loss, you don't need as robust a
> > > system as you would if you had a prolonged outage.
> > It's not a power loss issue (that would reset the entire PC)... the AC is an
> > inductive load on the mains and, as such, creates "spikes" on same when it's
> > turned off. These transients apparently travel across the DSL modem's power
> > supply and trip up the electronics inside.
> > See also http://www.intetron.com/technobabble.htm
> > That said, indeed seeing as this is not about surviving an outage per se, he
> > doesn't need an "oversized" system. He does need a "true" UPS, not a
> > standby/bypass model though.
> A good UPS, even a standby one, should have filtering and surge
> protection built-in. Some of the APC's have a sensitivity button on the
> back. Different level set at what point it will switch to battery. At it's
> most sensitive, even a half-wave missing will cause a switchover.
