Re: Adtran async/sync DSU 5600 with PM's

Jeremy Porter (jerry@fc.net)
Thu, 28 Sep 1995 11:40:55 -0500 (CDT)

>
>Steve Davies writes:
>> You are misinformed about V.34/V.34+ on two-wire. They are full-duplex.
>
>They are half-duplex.
>
>Just like any other analog modems, they can send information in only
>one direction at a time, which is the very definition of half duplex.

Gee, I guess the physics behind 300 baud and 1200 baud modems must
not apply to these V.34/V.34+, because those are full
duplex, using different carrier frequencies at the same time
to send data. V.32 uses a "trellis encoding" to use phase information
to transmit data, and can get higher bit rates out of the
same number of carrier bands. The DSP chips in the modems do
echo-canceling and phase equalization so that the phase information
is not destroyed.

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