ajayshah@alhena.usc.edu (Ajay Shah) (12/12/90)
(I don't read alt.fax, please email)
They say
"hi-resolution fax" is 200x100 dpi
"lo-resolution fax" is 100x100 dpi
Lets compute things for lo-res fax. 100x100 dpi is 1e4 bits per
square inch. A page is 11x9 inches is 100 square inches, or a
million bits.
A million bits is 125k. Being an image, it's not unreasonable to
expect compression downto 25k even costing for error detection
and correction.
Now if you have a 9600 baud modem, you are getting a throughput
of roughly 900 characters a second, so 25k should cost something
like 35 seconds. (So hi-res is 70 seconds)
Doesn't most fax transmission take a lot more?? Where did I screwup?
Further, how does one drive vanilla phone lines at 9600 baud?
Why does the telephone company blow bandwidth enough to support
9.6kb on each and every line when something like 2400 baud is
adequate for voice recognition by certain biological computers?
Come on, international lines are terrible on quality, (no way
they can allow 9600 baud or even 2400 baud logins) but faxes
seem to work fine. How is that achieved??
If the telephone company does, indeed, endow every line with
bandwidth enough to support 9.6kb, then does it mean we can just
plug in a 9.6kb modem into a vanilla telephone line and start
using a terminal??
Lastly, a question about PC-based fax card solutions: what
happens if a call comes in when the PC is switched off? Does the
fax-card have the capability to buffer a few pages locally using
a lithium battery types? When the PC is on, does the fax card
pickup the entire message in the background and then alert you
when it's ready to show you the pages? Or does it appropriate
the machine the moment a message starts coming in? Do the fax
cards allow 9.6kb serial port usage as a terminal?
Lastly, are there fax cards which accept postscript and emit
faxes?
Thanks,
-ans.
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Ajay Shah, (213)734-3930, ajayshah@usc.edu
The more things change, the more they stay insane.
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