On (17 Mar 96) Paul Edwards wrote to Arthur Marsh...



PE> Where did you get the softcopy from originally?  An FTP 

AM> I'd obtained it from the ITU document server before they 

AM> closed off access to their Recommendations.

PE> And you didn't get all the other specs at the time and keep 

PE> them in a safe place?  BFN.  Paul.

AM> Lots of others, just not all of them...

 PE> So, do you have any old electronic copies of any of the common

 PE> specs, ie V21, V22, V22bis, V32, V32bis, V34 that I could obtain?



Erm...  I don't think this reply will be what YOU are looking for (are you

after the original files?), but - what the hell :) BTW I take no blame for

any damage to erm...  Whatever might be damaged if what I am about to say is

wrong, either partially or completely... :)



V.21 - 300bps.  Uses Frequency Shift Keying (FSK) modulation, which encodes a

~~~~   single bit per baud.  Actual rate is 300 baud.



V.22 - 1200bps.  Fallback to 600bps.  Uses Differential-Phase Shift Keying

~~~~   (DPSK), which encodes two bits per baud.  Actual rate is 600 baud.



V.22bis - 2400bps.  Fallback to 1200bps.  Uses Quadrature Amplitude

~~~~~~~   Modulation (QAM), which encodes four bits per baud.  Actual rate is

          600 baud.



V.32 - 9600bps.  Fallback to 4800bps.  Uses Quadrature Amplitude Modulation

~~~~   (QAM) and (optionally) Trellis-Coded Modulation (TCM), which encodes

       four bits per baud.  Actual rate is 2400 baud.



V.32bis - 14400bps.  Fallback to 12000bps, 9600bps, 7200bps or 4800bps.  Uses

~~~~~~~   Quadrature Amplitude Modulation (QAM) and Trellis-Coded Modulation

          (TCM), which encodes six bits per baud.  Actual rate is 2400 baud.



[since my reference book doesn't have V.34, I'm going on what I have heard in

this echo and from other sources]



V.34 - 28800bps.  Fallback in 2400bps decrements right back to 2400bps (i.e.

~~~~   26400bps, 24000bps, 21600bps, 19200bps, etc.).  Uses types of

       modulatory techniques similar to V.32bis, but with trellis-precoding

       and line-probing (as well) to make the most of line-conditions.  The

       earlier standards did not adapt to line conditions, whereas V.34 will

       monitor conditions and adapt the signalling for best results.



Erm...  Some of those might be wrong, cuz I'm in a hurry - but hope I DID

help a little.  BTW if any of those are wrong, please don't complain :)



Chow.



Junyer Hakker.



... Backup not found: (A)bort (R)etry (P)anic



--- PPoint 1.92