1964 Antique MODEM Live Demo

[Dave McGuire]

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

-- 
Dave McGuire
Port Charlotte, FL