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Re: And we thought the text part of the Starr Report would be bad
- From: Eric Sobocinski
- Date: Wed Sep 23 17:26:18 1998
On Tuesday, 22 Sep 1998 at 22:43 EDT, Robert Szarka
>At 11:22 AM 9/22/98 , you wrote:
>> For modem to modem communications, start and stop bits were used
>> up through 2400 baud when one bit = one tone. The method of one
>> bit = one tone was dropped for other forms of encoding when modems
>> started supporting connection speeds in excess of 2400 baud.
>I assume you mean 2400 bps modems, i.e., v.22bis? Admittedly, it's been a
>while since I used one, but my recollection is that 2400 bps modems operate
>at 600 baud, with 4 bits/baud using QAM.
Your memory about v.22bis at 2400 bps is entirely correct. v.22 at
1200 bps/baud was the last of the 1 bps = 1 baud dialup modem standards. However, v.32/v.32bis/v.32ter/v.34/v.34bis all use trellis coding and
additional tricks to get high bit rates out of 2400 baud. It is
technically possible to get 2400 bps at 2400 baud from any of these
latter standards, though realistically the only place you'll find
conditions twisted enough to do that is in the lab.
--eric (speaking only on my own authority, as usual)