[Date Prev][Date Next] [Thread Prev][Thread Next] [Date Index] [Thread Index]

Re: 56K Modems



On Sun, Jan 04, 2004 at 09:04:49PM +0100, Arnt Karlsen wrote:
> On Sun, 4 Jan 2004 19:23:58 +0100, 
> Osamu Aoki <osamu@debian.org> wrote in message 
> <20040104182358.GB9012@aokiconsulting.com>:
> 
> > On Sat, Jan 03, 2004 at 02:31:12PM +0000, Pigeon wrote:
> > > On Fri, Jan 02, 2004 at 07:08:38PM -0800, Paul Johnson wrote:
> > > > -----BEGIN PGP SIGNED MESSAGE-----
> > > > Hash: SHA1
> > > > 
> > > > On Fri, Jan 02, 2004 at 02:13:12PM -0600, Jacob S. wrote:
> > > > > That's an interesting thought. Any recommendations for a good
> > > > > online store selling external modems in the UK?
> > > > 
> > > > I wouldn't bother.  The US dollar is super-weak right now, so a 25
> > > > pound modem is going to be more like $60, plus add $30 for
> > > > overseas shipping and whatever customs duties there might be.
> > > 
> > > Hmm, wonder if that's why they've got so cheap over here...
> > > 
> > 
> > Price is not all the issue here.
> > 
> > Most MODEM comes with AC adapter with transformer.  It is locked to AC
> > voltage and plug type.  UK != US  Just do not think about it.

I did mention this in my original post :-) I didn't consider the additional
cost of changing the adapter, as they're so cheap and widely available. I'd
be a bit surprised if they were significantly more expensive in the US.

> ..these usually states the low voltage ampereage and voltage too, like
> in "Input 230VAC ~ 50 Hz 20W, Output 13V =-=-= 1A 13VA ", or 
> "Input 230VAC ~ 50 Hz 75mW, Output 9VAC ~ 800mA 7.2VA", no?

Invariably, IME. I think it's a legal requirement.

> ..on replaceing the transformer adapter, you basically need to match the
> modems power demand, it should be printed in the docs or on the case.
> 
> ..the only showstoppers I can think of, is noise filters set to weed out
> 50Hz in the US and 60Hz elsewhere, and clock circuitry useing the
> power mains as a time source (hellooo!).  ;-)

s/US/UK/ In practical terms, if the smoothing can cope with 50Hz, it will
cope with 60Hz; it'll be in the adapter not the modem anyway; and it's
generally designed on the basis of "1000uF is big enough" :-)

Using the power mains as a time source is fine for things like
synchronous-motor-driven clocks (of the kind that humans tell the time
with), as long as you're in the right country; at least in the UK, the
frequency is legally required to average out to exactly 50Hz in a 24-hour
period. But all "computer-type" circuitry uses crystals, because (a) 50Hz is
too low a frequency to be much use, and (b) the short-term stability is
better from crystals. Also, it's difficult to get a time reference from DC...

-- 
Pigeon

Be kind to pigeons
Get my GPG key here: http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x21C61F7F

Attachment: pgpnEeSoyttw6.pgp
Description: PGP signature


Reply to: