On Feb 27, 1996 at 07:40, Bill Grimsley of 3:640/305.9 wrote:

 BG> # 25 Feb 09:58:12.16 Freq     Level
 BG> # 25 Feb 09:58:12.16  150     40
[...]
 BG> # 25 Feb 09:58:12.60 3750     59
 BG>
 BG> Basically, once the level drops below around -35dBm for a given frequency
 BG> (could be marginally higher at -33dBm, I'm not sure), the modems should

So "Freq" is in this case carrier frequency measured in hertz,
yes?  "Level" would therefore be measured -dBm?  Now is this
table telling me that at the time you issued the command to generate the
table, your USR estimated (experienced?  probed and discovered?  what?)
that for a frequency of "x" you would get (require?  what?) a
line level of "y" - yes or no?

So poor frequencies (as measured by the line level) are therefore 150Hz,
2,400Hz, 2,550Hz, 2,700Hz, 2,850Hz, 3,000Hz, 3,150Hz, 3,300Hz, 3,450Hz and
3,600Hz - yes?

Is the level the receive or transmit level?  The former, yes?

 BG> shift down to the next highest freq/level pair, and the above stats
 BG> indicate that the highest carrier frequency for a successful link is
 BG> around 2250Hz...

Okay, I can see this.

 BG> ...say 21600 or 24000 bps (or a step higher on modems
 BG> supporting 64-state trellis coding).

Does anyone know the approximate frequencies for each ITU-T recommended
speed?  How do you get 21.6Kbps from the table?  All my doco regarding bit
encoding into the carrier signal is dated 1990, and talks about 9.6Kbps
being "high speed".  :-(

 BG> The "V.34+" was basically USR's own working name for what
will soon be
 BG> ratified as V.34bis by the ITU-TSS (July 1996 is the expected date).

Didn't Arthur say that it'll still be "V.34", just a 1996 Annex?

 BG> That was common knowledge, so no surprises there at all.

Common expectation, but I wanted to confirm it.  My next question, of
course, is when the heck are Rockwell going to make their DSP Flash
upgradeable.  I guess NetComm finally going to Flash upgradeable ROMs is a
start, and gives some faint hope.  :-)

 db>> What, no sacrificial ropeless bungee from the window?!?!  ;-)
 BG> No, I'm not that cruel.  Unless, of course, you meant for Paul...  :)

That's always a possibility!  ;-)

    - dave
    d.begley{at}ieee.org

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