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Re: 56K Modems



On Sun, 4 Jan 2004 21:52:57 +0000, 
Pigeon <jah.pigeon@ukonline.co.uk> wrote in message 
<20040104215257.GB30783@droitwichbox.dyndns.org>:

> 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" :-)

.."oh, I thought mF meant micro Farad?".  ;-)

> 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

...and turning etch baths bowls...

> 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. 

..huh?  I thought the idea was to stick as close to 50Hz as possible?
On having some heavy gear hop onto the grid, the load slows it to 
say 49.99Hz, so promptly feeding more power onto the grid to bring 
it back up to 50Hz, is done. But you brits have to hike it up to say
50.01Hz for a while "to catch up lost clock time"???  
That too, is outside the 50Hz ideal.

> 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...

..100Hz to catch up in a day?  ;-)


-- 
..med vennlig hilsen = with Kind Regards from Arnt... ;-)
...with a number of polar bear hunters in his ancestry...
  Scenarios always come in sets of three: 
  best case, worst case, and just in case.



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