Re: TI-H: TI-Modem a reality
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Re: TI-H: TI-Modem a reality
Joe Martis wrote:
> I have figured out a way to make a modem type thing for the calculator,
> but it does not involve an evpensive modem. The way I see it is that the
> phone line uses two wires, right? The calc link uses two wires and a
> ground, right? I put two and two together and made a fuzzy picture. Slap
I can safely say that this project would be an utter failure. The
problem is
that the phone lines use varied voltages, somewhere around 90 volts (!)
when the phone is on hook and ~45 when off -- I'm not sure if I got
the numbers exactly right, but the point is, there is a huge difference
between a 5 volt TTL link port and the public phone network. Your
walkman has two power wires too, but that doesn't mean you should hook
it up to the 120 volt power grid!
> the red to the red, white to the green and make some software to do the
> rest. To ground the calculator's cable you can just wrap it, if you have
> something better, try it. If the phone line is a diffrent voltage that
I certainly hope you haven't tried this yet. It probably won't fry
your calculator or the phone network -- Since both are fairly well
protected, electrically -- but it would definitely not work.
And even if you did somehow isolate the lines, you still have the
hassle of converting digital data to an analog signal that can be
sent over the phone lines, and then there is dialing, detecting
a ring, and all of that. Put simply, you should be glad that
you can buy a 9600 baud modem surplus for $5 and have it do all of
this for you!
> the calculator we might have to do something about that (I don't know
> that much about this.) I find this relatively easy, excapt the software.
> It would use pulse dialing (unless if it can make more than one tone.)
> It must do protocoling. It must also do alot of other stuff. Since I
> don't know too much about this I'm leaving you guys to recearch it and
> develop it. Thanks for your time.
Its a good idea, but it would be a lot harder than just connecting
two wires together. I'm not even sure about the phone jack pinout, but I
can
assume that there are no digital lines on an analog phone jack. :-)
So essentially, it seems so much more reasonable to use a normal modem
and
connect your TI calculators via an ISP and the internet... using devices
which already have the bugs worked out.
Sorry to be such a spoilsport,
Bryan Rittmeyer
bryanr@flash.net
http://www.flash.net/~bryanr/extend/ <-- Cheap plug for my TI memory
expander project
References: