AVR-Chat

At 03:29 PM 4/9/2004 -0700, Dave Miller wrote:

>Hello Dave,
>
>Yes, it is Bell 202 and on a standard dialup.  We have a PDT that will
>replace the old Telxon acoustical terminals that have not been manufactured
>since the mid-90's.  Did you know that at any given time there is over 500K
>of these terminals in use today?  I was surprised by that number.

Ok, must be half duplex, that's trickier.
I'd think that you could do this with an AVR, supersampling at say 8x baud rate. That would detect distortion, before framing errors show up. 

The analog would be a little interesting, you'll need filters that don't distort the phase much.

>Anyways, my boss swears that back in the telxon days when he was in the
>field they used to use a Datascope of some kind that showed the signal and
>the data on the screen.  I am not sure if he meant the RS232 signal or the
>telco side.

Probably RS-232.

My own issue was with Verifone credit card terminals. 
We'd occasionally have problems where we weren't sure what exactly the host was sending, but what we received at the modem was definitely bad. 
So, the "Magic modem" was born. 

I think you could probably do the same thing for 202, provided you have an input that says "who's talking", or look at the signal amplitude, since the local end will be a lot hotter when it's talking, than the other end.