1964 Antique MODEM Live Demo

Dave McGuire mcguire at neurotica.com
Sun May 31 12:08:49 CDT 2009

On May 30, 2009, at 6:46 PM, Chris Elmquist wrote:
>> So, you can't see a possible set of circumstances where having the  
>> wrong
>> voltage coming in the serial port could cause the frequency shift  
>> to be
>> wrong?
>> How clever do you think the tone generator side is?
> Well, as Tony replied-- I think that the RS232 input is a logic level.
> It's not an analog level.  So, you are going to get either the mark  
> tone
> or the space tone and not something in between.
> I think this situation was just a poor explaination of what went  
> wrong.
> Whatever miscable situation he had caused him to generate the opposite
> tone of what he was expecting but not a tone that was off frequency  
> from
> one of the two possibilities.

   Was it in fact the opposite tones (i.e., mark/space reversed) or  
could it have been an originate mode vs. answer mode issue?  Many  
(most?) modems could be switched between the two sets of tones.


Dave McGuire
Port Charlotte, FL

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