AVR-Chat

>
>I am not up to speed on all the meanings behind some of the telco terminology so when I look at the equipment that is available now I can t find something that simply allows me to plug in my telco line then pass it on to the modem.  Or lets me tap into my RS232 line and displays the data.  There is a lot of fancy equipment that is designed for T1, DSL, etc& but I can t seem to figure out if it will do something this simple.

AFAIK, there isn't any such beast.

Are you sure you mean 202 as opposed to 212?
202 is FSK, for four wire interfaces.
212 is phase modulated, for dialup use.


I did a box for 212 years ago, using a pair of modem chips and an inductive coupling for debugging point of sale terminals.

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.

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.

Thanks,
Dave Miller

> -----Original Message-----
> From: David VanHorn [mailto:dvanhorn@cedar.net]
> Sent: Friday, April 09, 2004 3:23 PM
> To: AVR-Chat@yahoogroups.com; AVR-Chat@yahoogroups.com
> Subject: Re: [AVR-Chat] [OT] Test equipment question
> 
> 
> >
> >I am not up to speed on all the meanings behind some of the telco
> terminology so when I look at the equipment that is available now I can t
> find something that simply allows me to plug in my telco line then pass it
> on to the modem.  Or lets me tap into my RS232 line and displays the data.
> There is a lot of fancy equipment that is designed for T1, DSL, etc& but I
> can t seem to figure out if it will do something this simple.
> 
> AFAIK, there isn't any such beast.
> 
> Are you sure you mean 202 as opposed to 212?
> 202 is FSK, for four wire interfaces.
> 212 is phase modulated, for dialup use.
> 
> 
> I did a box for 212 years ago, using a pair of modem chips and an
> inductive coupling for debugging point of sale terminals.
> 
> 
> 
> 
> 
> 
> Yahoo! Groups Links
> 
> 
> 
>

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.

Here's a link to a company selling Bell 202 (leased line) modems:
http://www.data-linc.com/llm1100.htm

Hope that helps.

Regards,
   JJ

On Friday, Apr 9, 2004, at 18:15 US/Eastern, Dave Miller wrote:

> Hello All,
>
>  
>
> I am in need of analyzing some serial data. I am looking for the 
> ability to watch the rs232 data as well as have the ASCII/Hex 
> characters show up on the display.  I am interested in such things as 
> framing errors, parity errors, etc…
>
>  
>
> Actually the ideal test equipment would let me see the data on the 
> telephone side of the modem. 
>
>  
>
> My application is kind of old school technology but it is still used a 
> lot today.  We have a device that has an acoustical modem that 
> transmits at 1200 Baud using theBell202 standard.  We are having a 
> problem with some characters getting corrupted and we are trying to 
> analyze what is happening.  My receiving modem is an external modem so 
> it is no problem to watch the data on the RS232 side.  But we believe 
> we have an issue with noise being generated by our device due to the 
> way we are driving the speaker.  So if we are watching the data on the 
> output of the modem we probably won’t see the noise only the errors 
> created by the noise.
>
>  
>
> I am not up to speed on all the meanings behind some of the telco 
> terminology so when I look at the equipment that is available now I 
> can’t find something that simply allows me to plug in my telco line 
> then pass it on to the modem.  Or lets me tap into my RS232 line and 
> displays the data.  There is a lot of fancy equipment that is designed 
> for T1, DSL, etc… but I can’t seem to figure out if it will do 
> something this simple.
>
>  
>
> Any pointers to manufacturer and model of some good equipment for this 
> application would be great.  I am interested in what’s new on the 
> market and what is no longer made but can be purchased surplus.  Most 
> of the people I talk to tell me the equipment I need has not been made 
> for 10 years or more.
>
>  
>
> Thanks,
>
> Dave Miller
>
>  
>
>
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