Actually, Bell 202 has the option (it has so many options!!) of a backchannel
running at 5 bps which is amplitude modulated. Few Bell-202 modems support it,
and no-one has asked for it, so we are not working on it.

In addition to Bell-202, we have also developed Bell-103 (300bps FD) and V.23
(FD - 1200bps TX, 75bps RX) solutions using the Scenix SX28, and even have
these designs FCC qualified, and are capable of DTMF decoding and Type I
Caller ID. A V.22 (DPSK 1200bps FD) design is coming soon...

Stephen

Eric Smith <eric@BROUHAHA.COM> wrote:
> tmariner <tmariner@OPTONLINE.NET> wrote:
> > If you really need a modem -- I believe all standards up to 1200 bps
require
> > no phase decoding and are simple "mark space" FM encoding.
> 
> That's true of Bell 103 (300 BPS full-duplex, sometimes usable to 450 BPS
full
> duplex), and Bell 202 (1200 BPS half-duplex).
> 
> But all of the 1200 BPS full-duplex standards (Bell 212, Vadic 3400, CCITT
> V.22?) use either PSK or QAM.
> 
> Circuit Cellar INK recently published a design by Steven Holland of Scenix
> for a Bell 202 compatible modem based on the Scenix SX.  It's half-duplex,
> but leaves enough CPU cycles and memory space available that it can be
> integrated into a larger application.
> 
> Note that some implementations of Bell 202 allowed for a 75 bps back
channel,
> so they were somewhat full duplex.  I'm not sure whether that is actually
> part of the 202 specs.  I don't recall seeing this feature in Steven's
> design, but perhaps it is possible to add it.


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