x2, Testing your phone lines (above the USR Line Test)

x2, Testing your phone lines (above the USR Line Test)

Post by Dapper Da » Wed, 26 Nov 1997 04:00:00



I Finally got fed up and called USR for my Sportster 56k x2 modem.  This is
what they told me the problem was.  First you should do two differents
tests, the first being the USR line test to see if your phone lines are x2
capable (described below).  I assume it tests to see if there is more than
one analog segment connecting to the telco.  If you get a response that the
lines are x2 capable then you can proceed to the second test (also described
below).  If you don't get a response that the line is x2 capable then try
the test a few more times (it's a toll free number), or try a different line
if you have more than one line.

Line test:
   Using a terminal program (Hyperterminal, Rapid Comm, etc.) dial into
1-888-877-9248.  Hit enter at the graphics question, Then type "Line Test"
(w/o the quotes) at the name spot.  It will give you the results w/ a graph
and some other data.  Repeat as needed (you will need to dial in each time).

Other test: (You must have an x2 modem to do this and connect to an x2
server)
   Again using a terminal program, dial the USR BBS again (you can use the
same number as the Line Test).  Again hit enter at the graphics question,
but instead of typing line test wait at least a minute (but not long enough
to be disconnected).  Type "+++" (w/o the quotes... AND DO NOT HIT
RETURN/ENTER) and wait for the terminal to say ok.  Then type in
"ATI4I6I7I11Y11" (again w/o the quotes, and the I is a capital i, not a
lower case L), and hit return/enter.  You will get a long list of results
(you should try and capture this to a printer if possible so you can look at
all the results).

After doing this test myself and calling USR, the tech support girl asked me
for three results.  The first was the "Round Trip Delay (msec)" found near
the bottom just before the two column list of numbers.  Mine was 34, she
told me this was way too high, it had to be less than 15.  Then she asked me
for the "3750" Freq, at the very bottom of your results.  Mine was 62, she
told me this had to be less than 45.  Then she asked me for the "3300" Freq,
up the columb a little bit.  Mine was 36, she told me this had to be less
than 20.

She then went on to tell me that it was my phone lines even though I got
that x2 was possible w/ the line test.  She told me there was too much noise
on the line, to call my phone companies repair service and have them fix the
lines.

So I called the phone company (again) and told them there was too much noise
on the lines for my modem to work properly.  They said they would check the
lines to make sure it was not something inside my house, and would let me
know.  With my luck it will be the inside wiring, and I will need to contact
my landlord to get them to replace the inside lines (they are very old, you
can tell by looking at the wall outlets).  If it's neither the inside or
outside lines, then the phone company suggested I request a "data line".
This is basically paying them to "clean up" my phone connection to the
office to get rid of the noise (it is not an ISDN line).  They want $260 for
this.  Yeah like I'm going to pay that for them to fix "Their" lines when I
am not even going to be living here for more than another 1 1/2 years.

I am considering going to the local cable company for phone service (the
connection is made over the cable line instead of the phone co line, at
least to the cable office, but this is not a cable modem).  So maybe
everyone should think about a different phone company, if it's possible in
your area.

I hope this helped everyone w/ an x2 modem that was having problems.

Dave

 
 
 

x2, Testing your phone lines (above the USR Line Test)

Post by Dave Leepe » Thu, 27 Nov 1997 04:00:00



> I Finally got fed up and called USR for my Sportster 56k x2 modem.  This is
> what they told me the problem was.  First you should do two differents
> tests, the first being the USR line test to see if your phone lines are x2
> capable (described below).  
[snip]

> I hope this helped everyone w/ an x2 modem that was having problems.

> Dave


Dave (Dapper Dan) --

THANK YOU for a truly useful post.  I bought an X2 sportster this
afternoon and I'm surprised & disappointed to see connection speeds no
better than my old 28.8 modem.  Typical connect speeds to three
different ISPs have been 21600 to 24000.  Phooey.

I tried the USR line test several times & got two "Supports X2", three
"Can't support X2, and two "Impaired" ratings (Codes 1, 2, 3,
respectively).  

The real info was in the second test you described.  I used to do some
line performance measurements when I worked for Bell Labs, and I
interpret the technician's comments to you as follows (this is based on
old recollections, so please take it as an informed guess):

When she said round-trip delay had to be less than 15 milliseconds, I
think she was using this delay as a surrogate for counting the number of
analog-digital and digital-analog conversions.  Each of these
contributes distortion (called quantizing noise) *and* delay.  Ordinary
"flat" delay is not a problem, but the quantizing noise is.  At Bell
Labs, when we measured round-trip *cross-country* delay in 1982, a
typical value was 33 msec.  My modem reported a whopping 66 msec.  So I
presume I have many extra A/D and D/A conversions.

The "3750" number is the loss in decibels at 3750 Hz.  This is the very
upper edge of the voice band frequencies.  My modem showed 63 dB of
loss.  That's 18 dB more loss than the maximum she described to you.  To
pump 56K, the modem needs to squeeze every bit of bandwidth out that it
can, particularly at the higher frequencies.

The "3300" number is also fairly high in the band.  I only had 32 dB of
loss there, vs your 36, but we're both much worse than the 20 she called
for.  In fact, the lowest loss in the whole range was still 23 dB, at
900 Hz.  So I think I have a problem with a weak signal across the band.

Well the phone company is under no obligation to fix any of these
problems.  Those higher frequencies aren't needed at all for voice. My
voice service is just fine, and that's all I'm paying for.  I guess I'll
return the modem, curse my luck at the phone plant I got stuck with, and
wait, wait, wait for the cable company or xDSL service.  Bummer.

But your post has saved me several more hours of futile
experimentation.  Thanks again!

Regards,
Dave Leeper

 
 
 

1. USR Line Test says x2 capable but can't connect to ISP above 28.8

[snip]

:>

Its not going to happen. Why? The phone companies will tell you they gaurantee
line conditions for 9600 baud, no more, and that if you need to do any type of
communication beyond that the solution is ISDN.

The problem with the line test is that it only tells you if you can get an x2
connection from your location to the long distance number you are dialing. Copper
lines go to your local phone switch, phone switch is digital and routes your call
long distance to the USR modem pool which accepts the calls.

If you place a local call to your Internet provider,
the path your call takes can be very different, i.e, traversing more analog paths
locally from one town to the next.
That seems to be the problem you are experiencing here. By the way, you _can_
attain an x2 connection with more than one analog conversion.. in fact, with many,
although it will be poor. Too many, and you will only get an x2 connection sometimes
if at all.

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