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From: kolstad@cat21.cs.wisc.edu (Joel Kolstad)
Newsgroups: comp.sys.handhelds
Subject: Re: HP48 serial voltages (Question)
Keywords: RS232 HP48 SX
Message-ID: <4829@daffy.cs.wisc.edu>
Date: 8 May 90 22:40:50 GMT
References: <157.26454f66@wsuiar.uucp>
Sender: news@daffy.cs.wisc.edu
Organization: U of Wisconsin CS Dept
Lines: 27

In article <157.26454f66@wsuiar.uucp> maybe@igloo.scum.com (Jordan Gottlieb) writes:
>
>The low voltage of the HP seems to be the reason that it simply won't
>communicate with my computer.  I have a Toshiba 1200HB Laptop, and perhaps
>to save battery power or money the serial port is not as sensitive as
>it should be.  The calculator recieves text Xmited but somewhat garbled.{u!
>The Computer recieves nothing.  What can I do?
>How can I tell Toshiba that my serial port works with my modem, mouse,
>but not HP48sx and therefore I want them to do something about it?
>

Unfortunately, I don't think you're going to get Toshiba (or HP, for that
matter :-) ) to change.  If you're really desparate about getting your 48 to
talk to your Toshiba, you can build a tiny box to kick the +/- 4 up to +/- 12
volts.  I'd recommand using a Max-232, but that'd be wasting half the chip,
and if I recall correctly, you don't get +/- 12 out of that either!  So, you
need to do something quick and dirty like using a 1458 as a comparator.  If you
need more info, try mailing me...  my mail to you bounces!  In fact, if you 
want to help support a starving college student, I could even build you one
for less than the cost of a good pizza! (Apologies to all those out there who
hate commercial messages in posts!)  Try mailing me if you want more details
of how to build something like this or whatever.

					---Joel Kolstad

Gosh darn.  No .signature yet.  Well, hey, I don't take responsibility for 
anything, ever, period.  So there! :P